ORCID Profile
0000-0002-5679-8205
Current Organisation
Australian National University
Does something not look right? The information on this page has been harvested from data sources that may not be up to date. We continue to work with information providers to improve coverage and quality. To report an issue, use the Feedback Form.
Research Topics
In Research Link Australia (RLA), "Research Topics" refer to ANZSRC FOR and SEO codes. These topics are either sourced from ANZSRC FOR and SEO codes listed in researchers' related grants or generated by a large language model (LLM) based on their publications.
Top 5 Research Topics
ANZSRC Field of Research (FoR)
Theoretical and Computational Chemistry | Reaction Kinetics And Dynamics | Catalytic Process Engineering | Nanotechnology | Atmospheric Sciences | Climate Change Processes | Quantum Chemistry | Theory Of Materials | Theoretical and Computational Chemistry not elsewhere classified | Condensed Matter Modelling and Density Functional Theory | Biological And Medical Chemistry | Colloid And Surface Chemistry | Quantum Chemistry | Information Systems | Materials Engineering not elsewhere classified | Condensed Matter Physics not elsewhere classified | Software Engineering | Information Systems Organisation | Functional Materials | Nanotechnology | Resources Engineering and Extractive Metallurgy | Mineral Processing | Materials Engineering | Ceramics | Global Information Systems | Environmental Technologies | Civil Engineering | Chemical Engineering | Nanomaterials | Construction Engineering | Process Control And Simulation | Membrane And Separation Technologies
ANZSRC Socio-Economic Objective (SEO)
Chemical sciences | Expanding Knowledge in the Chemical Sciences | Biological sciences | Physical sciences | Climate Change Models | Expanding Knowledge in the Physical Sciences | Information processing services | Hydrogen-based Energy Systems (incl. Internal Hydrogen Combustion Engines) | Climate change | Solid Oxide Fuel Cells | Environmentally Sustainable Energy Activities not elsewhere classified | Integrated Circuits and Devices | Technological and organisational innovation | Plastic products (incl. Construction materials) | Energy storage | Expanding Knowledge in Technology | Hydrogen Production from Renewable Energy | Energy transformation not elsewhere classified | Industrial chemicals and related products | Solar-Photovoltaic Energy |
Related Links
Publications
Potential of Human Fetal Chorionic Stem Cells for the Treatment of Osteogenesis Imperfecta
Publisher: Mary Ann Liebert Inc
Date: 02-2014
Energy dependent dynamics of the O(1D) + HCl reaction: A quantum, quasiclassical and statistical study
Publisher: Royal Society of Chemistry (RSC)
Date: 2011
DOI: 10.1039/C0CP02619K
Abstract: The dynamics of the reaction O((1)D) + HCl → ClO + H, OH + Cl has been investigated in detail by means of a time-dependent wave packet (TDWP) method in comparison with quasiclassical trajectory (QCT) and statistical approaches on the ground potential energy surface by Martínez et al. [Phys. Chem. Chem. Phys., 2000, 2, 589]. Fully coupled quantum mechanical (QM) reaction probabilities for high values of the total angular momentum (J≤ 50) are reported for the first time. At the low collision energy regime (E(c)≤ 0.4 eV) the TDWP probabilities are well reproduced by the QCT and statistical results for the ClO forming product channel, but for the OH + Cl arrangement, only QCT probabilities are found to agree with the QM values. The good accordance found between the rigorous statistical models and the dynamical QM and QCT calculations for the O + HCl → ClO + H process underpins the assumption that the reaction pathway leading to ClO is predominantly governed by a complex-forming mechanism. In addition, to further test the statistical character of this reaction channel, the laboratory angular distribution and time-of-flight spectra obtained in a crossed molecular beam study by Balucani et al. [Chem. Phys. Lett. 1991, 180, 34] at a collision energy as high as 0.53 eV have been simulated using the state resolved differential cross section obtained with the statistical approaches yielding a satisfactory agreement with the experimental results. For the other channel, O + HCl → OH + Cl, noticeable differences between the statistical results and those found with the QCT calculation suggest that the dynamics of the reaction are controlled by a direct mechanism. The comparison between the QCT and QM-TDWP results in the whole range of collision energies lends credence to the QCT description of the dynamics of this reaction.
Anatase TiO2 single crystals with a large percentage of reactive facets
Publisher: Springer Science and Business Media LLC
Date: 05-2008
DOI: 10.1038/NATURE06964
Abstract: Owing to their scientific and technological importance, inorganic single crystals with highly reactive surfaces have long been studied. Unfortunately, surfaces with high reactivity usually diminish rapidly during the crystal growth process as a result of the minimization of surface energy. A typical ex le is titanium dioxide (TiO2), which has promising energy and environmental applications. Most available anatase TiO(2) crystals are dominated by the thermodynamically stable {101} facets (more than 94 per cent, according to the Wulff construction), rather than the much more reactive {001} facets. Here we demonstrate that for fluorine-terminated surfaces this relative stability is reversed: {001} is energetically preferable to {101}. We explored this effect systematically for a range of non-metallic adsorbate atoms by first-principle quantum chemical calculations. On the basis of theoretical predictions, we have synthesized uniform anatase TiO(2) single crystals with a high percentage (47 per cent) of {001} facets using hydrofluoric acid as a morphology controlling agent. Moreover, the fluorated surface of anatase single crystals can easily be cleaned using heat treatment to render a fluorine-free surface without altering the crystal structure and morphology.
Methane activation on Fe-4 cluster: A density functional theory study
Publisher: Elsevier BV
Date: 10-2012
Computational Materials Science: Discovering and Accelerating Future Technologies
Publisher: Wiley
Date: 03-2019
Calculation of resonances and product state distributions for the unimolecular dissociation of H2S
Publisher: American Chemical Society (ACS)
Date: 06-2002
DOI: 10.1021/JP013919T
Processable Surface Modification of Nickel‐Heteroatom (N, S) Bridge Sites for Promoted Alkaline Hydrogen Evolution
Publisher: Wiley
Date: 08-01-2019
Abstract: Nickel-heteroatoms bridge sites are important reaction descriptors for many catalytic and electrochemical processes. Herein we report the controllable surface modification of nickel-nitrogen (Ni-N) bridge sites on metallic Ni particles via a simplified vapor-assisted treatment approach. X-ray absorption spectroscopy (XAS) and Operando Raman spectroscopy verifies the interaction between Ni and surface-anchored N, which leads to distorted Ni lattice structure with improved wettability. The Ni-N bridge sites with appropriate N coverage level plays a critical role in the enhanced hydrogen evolution reaction (HER) and the optimized electrode (Ni-N
Rapid algorithms for microcanonical variational Rice-Ramsperger-Kassel-Marcus theory
Publisher: American Chemical Society (ACS)
Date: 07-1993
DOI: 10.1021/J100129A018
Encapsulated Silicene: A Robust Large-Gap Topological Insulator
Publisher: American Chemical Society (ACS)
Date: 25-08-2015
Abstract: The quantum spin Hall (QSH) effect predicted in silicene has raised exciting prospects of new device applications compatible with current microelectronic technology. Efforts to explore this novel phenomenon, however, have been impeded by fundamental challenges imposed by silicene's small topologically nontrivial band gap and fragile electronic properties susceptible to environmental degradation effects. Here we propose a strategy to circumvent these challenges by encapsulating silicene between transition-metal dichalcogenides (TMDCs) layers. First-principles calculations show that such encapsulated silicene exhibit a two-orders-of-magnitude enhancement in its nontrivial band gap, which is driven by the strong spin-orbit coupling effect in TMDCs via the proximity effect. Moreover, the cladding TMDCs layers also shield silicene from environmental gases that are detrimental to the QSH state in free-standing silicene. The encapsulated silicene represents a novel two-dimensional topological insulator with a robust nontrivial band gap suitable for room-temperature applications, which has significant implications for innovative QSH device design and fabrication.
Stacking-Dependent Interlayer Magnetic Coupling in 2D CrI3/CrGeTe3 Nanostructures for Spintronics
Publisher: American Chemical Society (ACS)
Date: 11-12-2019
Surface Reconstruction of Ultrathin Palladium Nanosheets during Electrocatalytic CO2 Reduction
Publisher: Wiley
Date: 17-09-2020
STATISTICAL MODELING OF ION-MOLECULE ELECTROSTATIC CAPTURE
Publisher: AIP Publishing
Date: 15-10-1992
DOI: 10.1063/1.463804
Abstract: A statistical model is presented which enables rapid and accurate calculation of capture rate coefficients for the interaction of ions with neutrals possessing any combination of dipole, quadrupole, and isotropic or anisotropic induced-dipole moments. Rate coefficients at very low temperatures are calculated via the state-resolved statistical adiabatic channel model (SACM). At higher temperatures, a classical state-counting technique is utilized which may be derived either from microcanonical variational transition state theory or from the high-temperature limit of the quantized SACM approach. The predicted rate coefficients are generally accurate to within 10% in comparison with classical trajectory calculations.
Super-Exchange Interaction Induced Overall Optimization in Ferromagnetic Perovskite Oxides Enables Ultrafast Water Oxidation
Publisher: Wiley
Date: 12-08-2019
Abstract: Oxygen evolution reaction (OER) is crucial in many renewable electrochemical technologies including regenerative fuel cells, rechargeable metal-air batteries, and water splitting. It is found that abundant active sites with favorable electronic structure and high electrical conductivity play a dominant role in achieving high electrocatalytic efficiency of perovskites, thus efficient strategies need to be designed to generate multiple beneficial factors for OER. Here, highlighted is an unusual super-exchange effect in ferromagnetic perovskite oxide to optimize active sites and enhance electrical conductivity. A systematic exploration about the composition-dependent OER activity in SrCo
Molecular dynamics and neutron scattering study of the dependence of polyelectrolyte dendrimer conformation on counterion behavior
Publisher: AIP Publishing
Date: 09-08-2012
DOI: 10.1063/1.4742190
Abstract: Atomistic molecular dynamics (MD) simulations and contrast variation small angle neutron scattering (SANS) have been combined to investigate the Generation-5 polyelectrolyte polyamidoamine starburst dendrimer. This work reveals the dendrimer conformational dependence on counterion association at different levels of molecular charge. The accuracy of the simulations is verified through satisfactory comparison between modeled results, such as excess intra-dendrimer scattering length density distribution and hydration level, and their experimental counterparts. While the counterion distributions are not directly measureable with SANS, the spatial distribution of the counterions and their dendrimer association are extracted from the validated MD equilibrium trajectories. It is found that the conformation of the charged dendrimer is strongly dependent on the counterion association. Sensitivity of the distribution of counterions around charged amines to the counterion valency is qualitatively explained by adopting Langmuir adsorption theory. Moreover, via extending the concept of electrical double layer for compact charged colloids, we define an effective radius of a charged dendrimer including the spatial distribution of counterions in its vicinity. Within the same framework, the correlation between the strength of intra-dendrimer electrostatic repulsion and the counterion valency and dynamics is also addressed.
MICROSCOPIC REACTION-RATES IN ION-MOLECULE REACTIONS - EFFECTS OF UNCOUPLED MODES
Publisher: American Chemical Society (ACS)
Date: 12-1989
DOI: 10.1021/J100362A005
New Family of Quantum Spin Hall Insulators in Two-dimensional Transition-Metal Halide with Large Nontrivial Band Gaps
Publisher: American Chemical Society (ACS)
Date: 04-11-2015
DOI: 10.1021/ACS.NANOLETT.5B02617
Abstract: Topological insulators (TIs) are promising for achieving dissipationless transport devices due to the robust gapless states inside the insulating bulk gap. However, currently realized two-dimensional (2D) TIs, quantum spin Hall (QSH) insulators, suffer from ultrahigh vacuum and extremely low temperature. Thus, seeking for desirable QSH insulators with high feasibility of experimental preparation and large nontrivial gap is of great importance for wide applications in spintronics. On the basis of the first-principles calculations, we predict a novel family of 2D QSH insulators in transition-metal halide MX (M = Zr, Hf X = Cl, Br, and I) monolayers, especially, which is the first case based on transition-metal halide-based QSH insulators. MX family has the large nontrivial gaps of 0.12-0.4 eV, comparable with bismuth (111) bilayer (0.2 eV), stanene (0.3 eV), and larger than ZrTe5 (0.1 eV) monolayers and graphene-based sandwiched heterstructures (30-70 meV). Their corresponding 3D bulk materials are weak topological insulators from stacking QSH layers, and some of bulk compounds have already been synthesized in experiment. The mechanism for 2D QSH effect in this system originates from a novel d-d band inversion, significantly different from conventional band inversion between s-p, p-p, or d-p orbitals. The realization of pure layered MX monolayers may be prepared by exfoliation from their 3D bulk phases, thus holding great promise for nanoscale device applications and stimulating further efforts on transition metal-based QSH materials.
Charge carrier exchange at chemically modified graphene edges: a density functional theory study
Publisher: Royal Society of Chemistry (RSC)
Date: 2012
DOI: 10.1039/C2JM30387F
Quantum dynamical characterization of unimolecular resonances
Publisher: Royal Society of Chemistry (RSC)
Date: 28-02-2003
DOI: 10.1039/B300284P
Adsorption and Dissociation of Ammonia Borane Outside and Inside Single-Walled Carbon Nanotubes: A Density Functional Theory Study
Publisher: American Chemical Society (ACS)
Date: 06-06-2011
DOI: 10.1021/JP2036026
Understanding the Charge Transfer at the Interface of Electron Donors and Acceptors: TTF–TCNQ as an Example
Publisher: American Chemical Society (ACS)
Date: 02-08-2017
Abstract: Charge transfer between an electron donor and an electron acceptor is widely accepted as being independent of their relative configurations if the interaction between them is weak however, the limit of this concept for an interacting system has not yet been well established. Our study of prototypical electron donor-acceptor molecules, tetrathiafulvalene-tetracyanoquinodimethane, using density functional theory based on an advanced functional, clearly demonstrates that for interacting molecules, their configurational arrangement is as important as their in idual electronic properties in the asymptotic limit to determine the charge transfer direction. For the first time, we demonstrate that by changing their relative orientation, one can reverse the charge transfer direction of the pair, causing the molecules to exchange roles as donor and acceptor. Our theory has important implications for understanding the interfacial charge-transfer mechanism of hybrid systems and related phenomena.
Restarted Krylov-space spectral filtering
Publisher: Royal Society of Chemistry (RSC)
Date: 1997
DOI: 10.1039/A606367E
Calculation of product state distributions from resonance decay via Lanczos subspace filter diagonalization: Application to HO2
Publisher: AIP Publishing
Date: 10-2001
DOI: 10.1063/1.1400785
Abstract: Resonance phenomena associated with the unimolecular dissociation of HO2 have been investigated quantum-mechanically by the Lanczos homogeneous filter diagonalization (LHFD) method. The calculated resonance energies, rates (widths), and product state distributions are compared to results from an autocorrelation function-based filter diagonalization (ACFFD) method. For calculating resonance wave functions via ACFFD, an analytical expression for the expansion coefficients of the modified Chebyshev polynomials is introduced. Both dissociation rates and product state distributions of O2 show strong fluctuations, indicating the dissociation of HO2 is essentially irregular.
SYNTHESIS AND BIOLOGICAL-ACTIVITY OF UNSYMMETRICAL BIS-STEROIDAL PYRAZINES RELATED TO THE CYTOTOXIC MARINE NATURAL PRODUCT CEPHALOSTATIN-1
Publisher: American Chemical Society (ACS)
Date: 11-1994
DOI: 10.1021/JO00101A052
Addition of diazomethane to armchair single-walled carbon nanotubes and their reaction sequences: A computational study
Publisher: Elsevier BV
Date: 02-2007
On the mechanism of gas adsorption for pristine, defective and functionalized graphene
Publisher: Royal Society of Chemistry (RSC)
Date: 2017
DOI: 10.1039/C6CP07654H
Abstract: Defects are no longer deemed an adverse aspect of graphene.
Structure, Dynamics, and Energetics of siRNA−Cationic Vector Complexation: A Molecular Dynamics Study
Publisher: American Chemical Society (ACS)
Date: 28-06-2010
DOI: 10.1021/JP911906E
Abstract: The design and synthesis of safe and efficient nonviral vectors for gene delivery has attracted significant attention in recent years. Previous experiments have revealed that the charge density of a polycation (the carrier) plays a crucial role in complexation and the release of the gene from the complex in the cytosol. In this work, we adopt an atomistic molecular dynamics simulation approach to study the complexation of short strand duplex RNA with six cationic carrier systems of varying charge and surface topology. The simulations reveal detailed molecular-level pictures of the structures and dynamics of the RNA-polycation complexes. Estimates for the binding free energy indicate that electrostatic contributions are dominant followed by van der Waals interactions. The binding free energy between the 8(+)polymers and the RNA is found to be larger than that of the 4(+)polymers, in general agreement with previously published data. Because reliable binding free energies provide an effective index of the ability of the polycationic carrier to bind the nucleic acid and also carry implications for the process of gene release within the cytosol, these novel simulations have the potential to provide us with a much better understanding of key mechanistic aspects of gene-polycation complexation and thereby advance the rational design of nonviral gene delivery systems.
Hexagonal honeycomb silicon: Silicene
Publisher: CRC Press
Date: 07-08-2017
Cell Membrane Penetration without Pore Formation
Publisher: Wiley
Date: 03-06-2020
Production and loss of HC3N in interstellar clouds: some relevant laboratory measurements
Publisher: Oxford University Press (OUP)
Date: 03-1986
First-principle study of adsorption of hydrogen on Ti-doped Mg(0001) surface
Publisher: American Chemical Society (ACS)
Date: 03-10-2006
DOI: 10.1021/JP063286O
Abstract: Ab initio density functional theory (DFT) calculations are performed to study the adsorption of H2 molecules on a Ti-doped Mg(0001) surface. We find that two hydrogen molecules are able to dissociate on top of the Ti atom with very small activation barriers (0.103 and 0.145 eV for the first and second H2 molecules, respectively). Additionally, a molecular adsorption state of H2 above the Ti atom is observed for the first time and is attributed to the polarization of the H2 molecule by the Ti cation. Our results parallel recent findings for H2 adsorption on Ti-doped carbon nanotubes or fullerenes. They provide new insight into the preliminary stages of hydrogen adsorption onto Ti-incorporated Mg surfaces.
STATISTICAL MODELING OF CAPTURE, ASSOCIATION, AND EXIT-CHANNEL DYNAMICS IN THE CH3+/CH3CN SYSTEM
Publisher: AIP Publishing
Date: 02-1993
DOI: 10.1063/1.464228
Abstract: The ion–molecule reaction CH3++CH3CN is known to have an association channel leading to CH3CNCH3+ in competition with the exothermic binary channels H2CN++C2H4 and C2H5++HCN. This reaction has been modeled using a master equation treatment incorporating weak collisions. The parameters required for the Rice–Ramsberger–Kassel–Marcus (RRKM) treatment have been found from an ab initio investigation of the CH3+/CH3CN energy surface. A means of including capture rate coefficients in the RRKM approach is developed, in which only the hindered dipole rotation is coupled with the reaction coordinate at large separations. Existing experimental data from ion cyclotron resonance (ICR) spectroscopy and a selected ion flow tube are fitted by the model in the pressure range 10−7–0.3 Torr. The low pressure experimental results are accounted for by weak collisions of the complex with the bath gas (when M=He, & ΔEdown≳ and & ΔRdown≳∼100 cm−1) corresponding to a collision efficiency β=0.05 for M=He and 0.14 for M=CH3CN. Unimolecular rate coefficients for the (CH3CNCH3+)* complex are calculated for all product channels at a range of temperatures from 300 to 600 K. The rate coefficient for radiative stabilization was found to be 225 s−1 at the conditions of the ICR experiment. The average lifetime of the complex was calculated to vary between 29 μs at 600 K to 0.47 ms at 300 K and the termolecular association rates from 3.4×10−24–9.8×10−23 cm6 s−1 (M=He) and from 6.7×10−23–2.2×10−21 cm6 s−1 (M=CH3CN) over the temperature range 600–300 K.
Angular momentum conservation in multichannel unimolecular reactions
Publisher: Wiley
Date: 12-1988
Structures, Energetics, and Electronic Properties of Layered Materials and Nanotubes of Cadmium Chalcogenides
Publisher: American Chemical Society (ACS)
Date: 21-11-2013
DOI: 10.1021/JP409772R
Application of inverse iteration to 2-dimensional master equations
Publisher: Wiley
Date: 06-1997
DOI: 10.1002/(SICI)1096-987X(199706)18:8<1004::AID-JCC4>3.0.CO;2-X
The catalytic role of an isolated-Ti atom in the hydrogenation of Ti-doped Al(001) surface: An ab initio density functional theory calculation
Publisher: Elsevier BV
Date: 12-2007
Bandgap narrowing of titanium oxide nanosheets: Homogeneous doping of molecular iodine for improved photoreactivity
Publisher: Royal Society of Chemistry (RSC)
Date: 2011
DOI: 10.1039/C1JM11295C
Multifunctional Porous Graphene for Nanoelectronics and Hydrogen Storage: New Properties Revealed by First Principle Calculations
Publisher: American Chemical Society (ACS)
Date: 15-02-2010
DOI: 10.1021/JA100156D
Abstract: The lack of an obvious "band gap" is a formidable hurdle for making a nanotransistor from graphene. Here, we use density functional calculations to demonstrate for the first time that porosity such as evidenced in recently synthesized porous graphene ( eleases/2009/11/091120084337.htm ) opens a band gap. The size of the band gap (3.2 eV) is comparable to most popular photocatalytic titania and graphitic C(3)N(4) materials. In addition, the adsorption of hydrogen on Li-decorated porous graphene is much stronger than that in regular Li-doped graphene due to the natural separation of Li cations, leading to a potential hydrogen storage gravimetric capacity of 12 wt %. In light of the most recent experimental progress on controlled synthesis, these results uncover new potential for the practical application of porous graphene in nanoelectronics and clean energy.
Understanding the enhancement in photoelectrochemical properties of photocatalytically prepared TiO 2-reduced graphene oxide composite
Publisher: American Chemical Society (ACS)
Date: 09-03-2011
DOI: 10.1021/JP1113575
Isomerization mechanism of the HcRed fluorescent protein chromophore
Publisher: Royal Society of Chemistry (RSC)
Date: 2012
DOI: 10.1039/C2CP41217A
Abstract: To understand how the protein achieves fluorescence, the isomerization mechanism of the HcRed chromophore is studied both under vacuum and in the solvated red fluorescent protein. Quantum mechanical (QM) and quantum mechanical/molecular mechanical (QM/MM) methods are applied both for the ground and the first excited state. The photoinduced processes in the chromophore mainly involve torsions around the imidazolinone-bridge bond (τ) and the phenoxy-bridge bond (φ). Under vacuum, the isomerization of the cis-trans chromophore essentially proceeds by τ twisting, while the radiationless decay requires φ torsion. By contrast, the isomerization of the cis-trans chromophore in HcRed occurs via simultaneous τ and φ twisting. The protein environment significantly reduces the barrier of this hula twist motion compared with vacuum. The excited-state isomerization barrier via the φ rotation of the cis-coplanar conformer in HcRed is computed to be significantly higher than that of the trans-non-coplanar conformer. This is consistent with the experimental observation that the cis-coplanar-conformation of the chromophore is related to the fluorescent properties of HcRed, while the trans-non-planar conformation is weakly fluorescent or non-fluorescent. Our study shows how the protein modifies the isomerization mechanism, notably by interactions involving the nearby residue Ile197, which keeps the chromophore coplanar and blocks the twisting motion that leads to photoinduced radiationless decay.
The effect of pH on PAMAM dendrimer–siRNA complexation — Endosomal considerations as determined by molecular dynamics simulation
Publisher: Elsevier BV
Date: 10-2011
DOI: 10.1016/J.BPC.2011.06.003
Abstract: Intracellular degradation of genes, most notably within the endo-lysosomal compartment is considered a significant barrier to (non-viral) gene delivery in vivo. Previous reports based on in vitro studies claim that carriers possessing a mixture of primary, secondary and tertiary amines are able to buffer the acidic environment within the endosome, allowing for timely release of their contents, leading to higher transfection rates. In this report, we adopt an atomistic molecular dynamics (MD) simulation approach, comparing the complexation of 21-bp siRNA with low-generation polyamidoamine (PAMAM) dendrimers (G0 and G1) at both neutral and acidic pHs, the latter of which mimics the degradative environment within maturing 'late-endosomes'. Our simulations reveal that the time taken for the dendrimer-gene complex (dendriplex) to reach equilibrium is appreciably longer at low pH and this is accompanied by more compact packaging of the dendriplex, as compared to simulations performed at neutral pH. We also note larger absolute values of calculated binding free energies of the dendriplex at low pH, indicating a higher dendrimer-nucleic acid affinity in comparison with neutral pH. These novel simulations provide a more detailed understanding of low molecular-weight polymer-siRNA behavior, mimicking the endosomal environment and provide input of direct relevance to the "proton sponge theory", thereby advancing the rational design of non-viral gene delivery systems.
Enhancing Cationic Drug Delivery with Polymeric Carriers: The Coulomb‐pH Switch Approach
Publisher: Wiley
Date: 21-12-2021
A comparison of low-storage strategies for spectral analysis in dissipative systems: filter diagonalisation in the Lanczos representation and harmonic inversion of the Chebychev-order-domain autocorrelation function
Publisher: Elsevier BV
Date: 10-2001
First-Principle Studies of the Formation and Diffusion of Hydrogen Vacancies in Magnesium Hydride
Publisher: American Chemical Society (ACS)
Date: 17-05-2007
DOI: 10.1021/JP072191Z
Catalytic effects of subsurface carbon in the chemisorption of hydrogen on a Mg(0001) surface: An ab-initio study
Publisher: American Chemical Society (ACS)
Date: 06-01-2006
DOI: 10.1021/JP055972D
Abstract: Ab initio density functional theory (DFT) calculations are performed to explore possible catalytic effects on the dissociative chemisorption of hydrogen on a Mg(0001) surface when carbon is incorporated into Mg materials. The computational results imply that a C atom located initially on a Mg(0001) surface can migrate into the subsurface and occupy an fcc interstitial site, with charge transfer to the C atom from neighboring Mg atoms. The effect of subsurface C on the dissociation of H2 on the Mg(0001) surface is found to be relatively marginal: a perfect sublayer of interstitial C is calculated to lower the barrier by 0.16 eV compared with that on a pure Mg(0001) surface. Further calculations reveal, however, that sublayer C may have a significant effect in enhancing the diffusion of atomic hydrogen into the sublayers through fcc channels. This contributes new physical understanding toward rationalizing the experimentally observed improvement in absorption kinetics of H2 when graphite or single walled carbon nanotubes (SWCNT) are introduced into the Mg powder during ball milling.
Theoretical investigation of the potential energy surface for the NH2+NO reaction via density functional theory and ab initio molecular electronic structure theory
Publisher: AIP Publishing
Date: 08-06-1997
DOI: 10.1063/1.474025
Abstract: The potential energy surface of the NH2+NO reaction, which involves nine intermediates (1–9) as well as twenty-three possible transition states (a–w), has been fully characterized at the B3LYP/cc-pVQZ//B3LYP/6-311G(d,p)+ZPE[B3LYP/6-311G(d,p)] and modified Gaussian-2 (G2M) levels of theory. The reaction is shown to have three different groups of products (HN2+OH, N2O+H2, and N2+H2O denoted as A, B, and C, respectively) and a very complicated reaction mechanism. The first reaction path is initiated by the N–N bond association of the reactants to form an intermediate H2NNO, 1, which then undergoes a 1,3-H migration to yield an isomer pair HNNOH (2,3) (separated by a low energy torsional barrier) which can then proceed along three different paths. Because of the essential role it would play kinetically, the enthalpy of the NH2+NO→HN2+OH reaction has been further investigated using various levels of theory. The best theoretical results of this study predicted it to be 0.9 and 2.4 kcal mol−1 at the B3LYP and CCSD(T) levels, respectively, using a relatively large basis set (AUG-cc-pVQZ) based on the geometry optimized at the B3LYP/6-311G(d,p) level of theory. It has been found that TS g(4→B) is expected to be the rate-determining transition state responsible for the NH2+NO→N2O+H2 reaction. TS g lies above the reactants by only 2.6 kcal mol−1 according to the G2M prediction. On the other hand, TS h(3→7) is a new transition state discovered in this work which may allow some kinetic contribution from the NH2+NO→N2+H2O reaction under high temperature conditions due to its relatively low energy as well as its loose transition state property. A modified G2 additivity scheme based on the G2(DD) approach has been shown to be necessary for better predicting the energetics for TS h, which gives a value of 2.3 kcal mol−1 in energy with respect to the reactants. Generally, the cost-effective B3LYP method is found to give very good predictions for the optimized geometries and vibrational frequencies of various species in the system if compare them with those optimized at the QCISD/6-311G(d,p) and 12-in-11 CASSCF/cc-pVDZ levels of theory. Furthermore, it is noticeable in this study that most of the relative energies calculated via the B3LYP method are more close to the G2M results than those predicted at the PMP4 and CCSD(T) levels using the same 6-311G(d,p) basis set.
Leading coordinate analysis of reaction pathways in proton chain transfer: Application to a two-proton transfer model for the green fluorescent protein
Publisher: Elsevier BV
Date: 07-2006
A CONVENIENT PROCEDURE FOR THE SYNTHESIS OF BIS-STEROIDAL PYRAZINES - MODELS FOR THE CEPHALOSTATINS
Publisher: American Chemical Society (ACS)
Date: 11-1992
DOI: 10.1021/JO00050A002
The 2.0 Å Crystal Structure of a Pocilloporin at pH 3.5: The Structural Basis for the Linkage Between Color Transition and Halide Binding
Publisher: Wiley
Date: 2006
Electrocatalytic Reduction of Carbon Dioxide to Methane on Single Transition Metal Atoms Supported on a Defective Boron Nitride Monolayer: First Principle Study
Publisher: Wiley
Date: 10-09-2018
Asymmetrically Decorated, Doped Porous Graphene As an Effective Membrane for Hydrogen Isotope Separation
Publisher: American Chemical Society (ACS)
Date: 09-03-2012
DOI: 10.1021/JP211930A
Exact and truncated Coriolis coupling calculations for the S(1D)+HD reaction employing the ground adiabatic electronic state
Publisher: Royal Society of Chemistry (RSC)
Date: 2010
DOI: 10.1039/C0CP00850H
Abstract: We present exact quantum differential cross sections and exact and estimated integral cross sections and branching ratios for the title reaction. We employ a time-dependent wavepacket method as implemented in the DIFFREALWAVE code including all Coriolis couplings and also an adapted DIFFREALWAVE code where the helicity quantum number and with this the Coriolis couplings have been truncated. Our exact differential cross sections at 0.453 eV total energy, one of the experimental energies, show good agreement with the experimental results for one of the product channels. While the truncated calculation present a significant reduction in the computational effort needed they overestimate the exact integral cross sections.
Multiple-well isomerization diffusion equation solutions with a shift and invert Lanczos algorithm
Publisher: American Chemical Society (ACS)
Date: 08-1997
DOI: 10.1021/JP970481H
Computational design of two-dimensional nanomaterials for charge modulated CO2 /H2 capture and/or storage
Publisher: Elsevier BV
Date: 07-2017
Recent developments in the quantum dynamical characterization of unimolecular resonances
Publisher: Royal Society of Chemistry (RSC)
Date: 2004
DOI: 10.1039/B315824A
Direct insights into the role of epoxy groups on cobalt sites for acidic H2O2 production
Publisher: Springer Science and Business Media LLC
Date: 21-08-2020
DOI: 10.1038/S41467-020-17782-5
Abstract: Hydrogen peroxide produced by electrochemical oxygen reduction reaction provides a potentially cost effective and energy efficient alternative to the industrial anthraquinone process. In this study, we demonstrate that by modulating the oxygen functional groups near the atomically dispersed cobalt sites with proper electrochemical/chemical treatments, a highly active and selective oxygen reduction process for hydrogen peroxide production can be obtained in acidic electrolyte, showing a negligible amount of onset overpotential and nearly 100% selectivity within a wide range of applied potentials. Combined spectroscopic results reveal that the exceptionally enhanced performance of hydrogen peroxide generation originates from the presence of epoxy groups near the Co–N 4 centers, which has resulted in the modification of the electronic structure of the cobalt atoms. Computational modeling demonstrates these electronically modified cobalt atoms will enhance the hydrogen peroxide productivity during oxygen reduction reaction in acid, providing insights into the design of electroactive materials for effective peroxide production.
Density functional theory study on adsorption of Pt nanoparticle on graphene
Publisher: Elsevier BV
Date: 05-2013
Cobalt-doped cadmium selenide colloidal nanowires
Publisher: Royal Society of Chemistry (RSC)
Date: 2011
DOI: 10.1039/C1CC13467A
Abstract: Co(2+)-doped CdSe colloidal nanowires with tunable size and dopant concentration have been prepared by a solution-liquid-solid (SLS) approach for the first time. These doped nanowires exhibit anomalous photoluminescence temperature dependence in comparison with undoped nanowires.
Application of contracted distributed approximating functions to solving vibrational eigenvalue problems
Publisher: AIP Publishing
Date: 1999
DOI: 10.1063/1.478086
Abstract: It has been shown that an approximately band-limited function can be reconstructed by using the function’s values taken at appropriate equidistant grid points and a generalized Hermite-contracted-continuous-distributed-approximating-function (Hermite-CCDAF) as the reconstruction function. A s ling theorem prescribing the possible choices of grid spacing and DAF parameters has been derived and discussed, and discretized-Hermite-contracted DAFs have been introduced. At certain values of its parameters the generalized Hermite-CCDAF is identical to the Shannon–Gabor-wavelet-DAF (SGWDAF). Simple expressions for constructing the matrix of a vibrational Hamiltonian in the discretized-Hermite-contracted DAF approximation have been given. As a special case the matrix elements corresponding to sinc-DVR (discrete variational representation) are recovered. The usefulness and properties of sinc-DVR and discretized-Hermite-contracted-DAF (or SGWDAF) in bound state calculations have been compared by solving the eigenvalue problem of a number of one- and two-dimensional Hamiltonians. It has been found that if one requires that the same number of energy levels be computed with an error less than or equal to a given value, the SGWDAF method with thresholding is faster than the standard sinc-DVR method. The results obtained with the Barbanis Hamiltonian are described and discussed in detail.
Band-to-Band Visible-Light Photon Excitation and Photoactivity Induced by Homogeneous Nitrogen Doping in Layered Titanates
Publisher: American Chemical Society (ACS)
Date: 10-03-2009
DOI: 10.1021/CM802986R
Policy Processes in Multisectoral Tobacco Control in India: The Role of Institutional Architecture, Political Engagement and Legal Interventions
Publisher: Maad Rayan Publishing Company
Date: 14-07-2021
Hydrogen Incorporation and Storage in Well-Defined Nanocrystals of Anatase Titanium Dioxide
Publisher: American Chemical Society (ACS)
Date: 07-12-2011
DOI: 10.1021/JP210472P
Control of Hopf Bifurcation and Chaos as Applied to Multimachine System
Publisher: Springer Netherlands
Date: 2011
Theoretical Predictions of Freestanding Honeycomb Sheets of Cadmium Chalcogenides
Publisher: American Chemical Society (ACS)
Date: 02-06-2014
DOI: 10.1021/JP504299E
Oxygen Electrocatalysis at MnIII–Ox–C Hybrid Heterojunction: An Electronic Synergy or Cooperative Catalysis?
Publisher: American Chemical Society (ACS)
Date: 30-11-2019
Abstract: The interface at the metal oxide-carbon hybrid heterojunction is the source to the well-known "synergistic effect" in catalysis. Understanding the structure-function properties is key for designing more advanced catalyst-support systems. Using a model Mn
Integral and differential cross sections for the S(1D)+HD reaction employing the ground adiabatic electronic state
Publisher: Royal Society of Chemistry (RSC)
Date: 2009
DOI: 10.1039/B917972K
Abstract: We present converged quantum mechanical calculations for the title reaction employing a time-dependent wavepacket method. We obtained integral and differential cross sections over an energy range from 0.23 to 0.35 eV total energy as well as product state distributions for both product channels. The excitation functions decrease with energy and point to statistical dynamics as do the cold vibrational distributions and highly inverted rotational distributions. The differential cross sections oscillate strongly with energy for both product channels. Our differential cross sections for both product channels at 2.5 kcal/mol, one of the experimental energies, compare well to the experimental results. The quantum results obtained in this study are similar to what has been found employing QCT methods, implying that the differences between the experimental and theoretical results are due to the potential energy surface or non-adiabatic effects rather than due to quantum effects or the methods employed.
A master equation model for bimolecular reaction via multi-well isomerizing intermediates
Publisher: Royal Society of Chemistry (RSC)
Date: 2000
DOI: 10.1039/A908180A
Growth and Electrochemical Characterization of Carbon Nanospike Thin Film Electrodes
Publisher: The Electrochemical Society
Date: 2014
DOI: 10.1149/2.0891409JES
Analytical description of nanowires. I. Regular cross sections for zincblende and diamond structures
Publisher: International Union of Crystallography (IUCr)
Date: 03-09-2019
DOI: 10.1107/S2052520619009351
Abstract: Semiconductor nanowires (NWires) experience stress and charge transfer from their environment and impurity atoms. In response, the environment of a NWire experiences a NWire stress response which may lead to propagated strain and a change in the shape and size of the NWire cross section. Here, geometric number series are deduced for zincblende- (zb-) and diamond-structured NWires of diameter d Wire to obtain the numbers of NWire atoms N Wire ( d Wire [ i ]), bonds between NWire atoms N bnd ( d Wire [ i ]) and interface bonds N IF ( d Wire [ i ]) for six high-symmetry zb NWires with the low-index faceting that occurs frequently in both bottom-up and top-down approaches of NWire processing. Along with these primary parameters, the specific lengths of interface facets, the cross-sectional widths and heights and the cross-sectional areas are presented. The fundamental insights into NWire structures revealed here offer a universal gauge and thus could enable major advancements in data interpretation and understanding of all zb- and diamond-structure-based NWires. This statement is underpinned with results from the literature on cross-section images from III–V core–shell NWire growth and on Si NWires undergoing self-limiting oxidation and etching. The massive breakdown of impurity doping due to self-purification is shown to occur for both Si NWires and Si nanocrystals (NCs) for a ratio of N bnd / N Wire = N bnd / N NC = 1.94 ± 0.01 using published experimental data.
HOCl Ro-Vibrational Bound-State Calculations for Nonzero Total Angular Momentum
Publisher: American Chemical Society (ACS)
Date: 04-03-2006
DOI: 10.1021/JP058286N
Abstract: The Lanczos homogeneous filter diagonalization method has been employed to compute the HOCl ro-vibrational states for a range of total angular momenta (J = 0, 1, 5, 10, 11, 20, 30) on a newly developed ab initio potential energy surface by Nanbu et al. (J. Theor. Comput. Chem. 2002, 1, 263). For such computationally challenging calculations, a parallel computing strategy has been incorporated into our method to perform the matrix-vector multiplications. For the computed low bound states, a spectroscopic assignment has been made and the widely used approximate adiabatic rotation method has been tested for the broad range of total angular momenta for this deep-well system. Comparison of experimental results with exact quantum mechanical calculations for the selected far-infrared transitions involving the range of total angular momenta has been made possible for the first time.
The noise properties of 42 millisecond pulsars from the European Pulsar Timing Array and their impact on gravitational-wave searches
Publisher: Oxford University Press (OUP)
Date: 07-03-2016
DOI: 10.1093/MNRAS/STW179
Computational study of methyl derivatives of ammonia borane for hydrogen storage
Publisher: Royal Society of Chemistry (RSC)
Date: 2008
DOI: 10.1039/B807776B
Abstract: The structures and thermodynamic properties of methyl derivatives of ammonia-borane (BH3NH3, AB) have been studied with the frameworks of density functional theory and second-order Møller-Plesset perturbation theory. It is found that, with respect to pure, methyl ammonia-boranes show higher complexation energies and lower reaction enthalpies for the release of H2, together with a slight increment of the activation barrier. These results indicate that the methyl substitution can enhance the reversibility of the system and prevent the formation of BH3/NH3, but no enhancement of the release rate of H2 can be expected.
Mechanistic aspects of proton chain transfer: A computational study for the green fluorescent protein chromophore
Publisher: American Chemical Society (ACS)
Date: 14-02-2006
DOI: 10.1021/JP056966K
Abstract: We explore several models for the ground-state proton chain transfer pathway between the green fluorescent protein chromophore and its surrounding protein matrix, with a view to elucidating mechanistic aspects of this process. We have computed quantum chemically the minimum energy pathways (MEPs) in the ground electronic state for one-, two-, and three-proton models of the chain transfer. There are no stable intermediates for our models, indicating that the proton chain transfer is likely to be a single, concerted kinetic step. However, despite the concerted nature of the overall energy profile, a more detailed analysis of the MEPs reveals clear evidence of sequential movement of protons in the chain. The ground-state proton chain transfer does not appear to be driven by the movement of the phenolic proton off the chromophore onto the neutral water bridge. Rather, this proton is the last of the three protons in the chain to move. We find that the first proton movement is from the bridging Ser205 moiety to the accepting Glu222 group. This is followed by the second proton moving from the bridging water to the Ser205--for our model this is where the barrier occurs. The phenolic proton on the chromophore is hence the last in the chain to move, transferring to a bridging "water" that already has substantial negative charge.
Tetragonal bismuth bilayer: A stable and robust quantum spin hall insulator
Publisher: IOP Publishing
Date: 23-11-2015
First principle study of hydrogenation of MgB 2 : An important step toward reversible hydrogen storage in the coupled LiBH 4 /MgH 2 system
Publisher: American Scientific Publishers
Date: 07-2009
DOI: 10.1166/JNN.2009.M65
Abstract: Recent experiments [F. E. Pinkerton, M. S. Meyer, G. P. Meisner, M. P. Balogh, and J. J. Vajo, J. Phys. Chem. C 111, 12881 (2007) and J. J. Vajo and G. L. Olson, Scripta Mater. 56, 829 (2007)] demonstrated that the recycling of hydrogen in the coupled LiBH4/MgH2 system is fully reversible. The rehydrogenation of MgB2 is an important step toward the reversibility. By using ab initio density functional theory calculations, we found that the activation barrier for the dissociation of H2 are 0.49 and 0.58 eV for the B and Mg-terminated MgB2(0001) surface, respectively. This implies that the dissociation kinetics of H2 on a MgB2(0001) surface should be greatly improved compared to that in pure Mg materials. Additionally, the diffusion of dissociated H atom on the Mg-terminated MgB2(0001) surface is almost barrier-less. Our results shed light on the experimentally-observed reversibility and improved kinetics for the coupled LiBH4/MgH2 system.
AN ASTEROID BELT INTERPRETATION FOR THE TIMING VARIATIONS OF THE MILLISECOND PULSAR B1937+21
Publisher: American Astronomical Society
Date: 28-02-2013
Sulfur doped anatase TiO2 single crystals with a high percentage of {001} facets
Publisher: Elsevier BV
Date: 09-2010
DOI: 10.1016/J.JCIS.2010.05.076
Abstract: Extending the response range of wide-bandgap (3.2 eV) anatase TiO(2) photocatalysts into the visible light range can play an important role in promoting the practical applications of photocatalysts. Here, we report a route to prepare sulfur doped anatase TiO(2) single crystal sheets with a high percentage of {0 0 1} facets. The resultant TiO(2) sheets were investigated by a combination of experimental characterizations and electronic structure calculations. The synthesized sulfur doped anatase s les show an additional visible light absorption band from 400 nm to ca. 550 nm and some visible-light photocatalytic activity in *OH radical generation and photodecomposition of organic dyes. The Ti-S bond structure causes not only visible light absorption but also changes to an extent the surface structures of doped anatase TiO(2) sheets. Theoretically, localized 3p states of S formed in the bandgap are implicated for the visible light absorption of the sulfur doped anatase TiO(2).
Pyrite-type ruthenium disulfide with tunable disorder and defects enables ultra-efficient overall water splitting
Publisher: Royal Society of Chemistry (RSC)
Date: 2019
DOI: 10.1039/C9TA04120F
Abstract: Synergistic disorder and defect engineering in ruthenium disulfide enables efficient water splitting with an ultralow cell voltage of 1.527 V.
The calculation of vibrational eigenstates by MINRES filter diagonalization
Publisher: Wiley
Date: 03-2010
Nitrogen Doped Carbon Nanosheets Coupled Nickel-Carbon Pyramid Arrays Toward Efficient Evolution of Hydrogen
Publisher: Wiley
Date: 19-07-2017
Materials design for electrocatalytic carbon capture
Publisher: AIP Publishing
Date: 23-02-2016
DOI: 10.1063/1.4942635
Abstract: We discuss our philosophy for implementation of the Materials Genome Initiative through an integrated materials design strategy, exemplified here in the context of electrocatalytic capture and separation of CO2 gas. We identify for a group of 1:1 X–N graphene analogue materials that electro-responsive switchable CO2 binding behavior correlates with a change in the preferred binding site from N to the adjacent X atom as negative charge is introduced into the system. A reconsideration of conductive N-doped graphene yields the discovery that the N-dopant is able to induce electrocatalytic binding of multiple CO2 molecules at the adjacent carbon sites.
Diluted Magnetic Semiconductor Nanowires Prepared by the Solution–Liquid–Solid Method
Publisher: Wiley
Date: 26-03-2010
Lithium-Catalyzed Dehydrogenation of Ammonia Borane within Mesoporous Carbon Framework for Chemical Hydrogen Storage
Publisher: Wiley
Date: 08-01-2009
Theoretical Studies of Chromophore Maturation in the Wild-Type Green Fluorescent Protein: ONIOM(DFT:MM) Investigation of the Mechanism of Cyclization
Publisher: American Chemical Society (ACS)
Date: 24-01-2012
DOI: 10.1021/JP208749V
Abstract: The availability of a gene encoding green fluorescence immediately stimulates interest in the puzzle of autocatalytic formation of the green fluorescent protein (GFP) chromophore. Numerous experimental and theoretical studies have indicated that cyclization is the first and most important step in the maturation process of the GFP. In our previous paper based on cluster models [J. Phys. Chem. B2010, 114, 9698-9705], two possible mechanisms have been investigated with the conclusion that the backbone condensation initiated by deprotonation of the Gly67 amide nitrogen is easier than deprotonation of the Tyr66 α-carbon. However, the impact of the protein environment on the reaction mechanism remains to be explored. In this paper, we investigated the two possible mechanisms with inclusion of protein environmental effects by using molecular dynamics (MD) and combined quantum mechanics/molecular mechanics (QM/MM) calculations. Our calculations reveal no hydrogen bonding network that would facilitate deprotonation of the amide nitrogen of Gly67, although it is the lower energy pathway in the cluster model system. Contrastingly, there is a hydrogen bonding network between Tyr66 α-carbon and Glu222, which is in good agreement with X-ray data. The ONIOM studies show that proton transfer from Tyr66 α-carbon to Glu222 is a long-distance charge transfer process. The charge distribution of the MM region has a significant perturbation to the wave function for the QM region, with the QM energy for the proton transfer product being increased under the influence of the electrostatic protein environment. The barrier for the rate-limiting step in cyclization is quite high, about 40.0 kcal/mol in the case of ONIOM-EE.
Phosphorene: Fabrication, Properties, and Applications
Publisher: American Chemical Society (ACS)
Date: 06-07-2015
DOI: 10.1021/ACS.JPCLETT.5B01094
Abstract: Phosphorene, the single- or few-layer form of black phosphorus, was recently rediscovered as a two-dimensional layered material holding great promise for applications in electronics and optoelectronics. Research into its fundamental properties and device applications has since seen exponential growth. In this Perspective, we review recent progress in phosphorene research, touching upon topics on fabrication, properties, and applications we also discuss challenges and future research directions. We highlight the intrinsically anisotropic electronic, transport, optoelectronic, thermoelectric, and mechanical properties of phosphorene resulting from its puckered structure in contrast to those of graphene and transition-metal dichalcogenides. The facile fabrication and novel properties of phosphorene have inspired design and demonstration of new nanodevices however, further progress hinges on resolutions to technical obstructions like surface degradation effects and nonscalable fabrication techniques. We also briefly describe the latest developments of more sophisticated design concepts and implementation schemes that address some of the challenges in phosphorene research. It is expected that this fascinating material will continue to offer tremendous opportunities for research and development for the foreseeable future.
Iterative quantum computations of HO2 bound states and resonances for J=4 and 5
Publisher: Royal Society of Chemistry (RSC)
Date: 2004
DOI: 10.1039/B407283A
Kinematic factors in transition state theory with a generalized reaction coordinate
Publisher: American Chemical Society (ACS)
Date: 21-09-2000
DOI: 10.1021/JP001120W
The role of V2 O5 on the dehydrogenation and hydrogenation in magnesium hydride: An ab initio study
Publisher: AIP Publishing
Date: 21-04-2008
DOI: 10.1063/1.2916828
Abstract: Ab initio density functional theory calculations are performed to study the experimentally observed catalytic role of V2O5 in the recycling of hydrogen in magnesium hydride. We find that the Mg–H bond length becomes elongated when MgH2 clusters are positioned on single, two, and three coordinated oxygen sites (O1, O2, and O3) on the V2O5(001) surface. Molecular hydrogen is predicted to spontaneously form at the hole site on the V2O5(001) surface. Additionally, the activation barrier for the dissociation of hydrogen on V-doped Mg(0001) surface is 0.20eV, which is only 15 of that on pure Mg(0001) surface. Our results indicate that oxygen sites on the V2O5(001) surface and the V dopant in Mg may be important facilitators for dehydrogenation and rehydrogenation, respectively. The understanding gained here will aid in the rational design and development of Mg-based hydrogen storage materials.
Circulants, symmetry and time-independent wavepacket scattering
Publisher: Elsevier BV
Date: 10-1999
Comparative study of hydrogen storage in Li- and K-doped carbon materials––theoretically revisited
Publisher: Elsevier BV
Date: 2004
Porous Graphene and Nanomeshes
Publisher: Wiley
Date: 09-08-2013
Versatile electrocatalytic processes realized by Ni, Co and Fe alloyed core coordinated carbon shells
Publisher: Royal Society of Chemistry (RSC)
Date: 2019
DOI: 10.1039/C9TA01723B
Abstract: Through encapsulation of Ni, Co and Fe alloyed core inside graphitic carbon shells, a versatile composite catalyst can be obtained that demonstrates excellent activity towards electrochemical energy conversion reactions.
Chemically modified ribbon edge stimulated H-2 dissociation: a first-principles computational study
Publisher: Royal Society of Chemistry (RSC)
Date: 2013
DOI: 10.1039/C3CP50654A
Abstract: First-principles computational studies indicate that (B, N, or O)-doped graphene ribbon edges can substantially reduce the energy barrier for H2 dissociative adsorption. The low barrier is competitive with many widely used metal or metal oxide catalysts. This suggests that suitably functionalized graphene architectures are promising metal-free alternatives for low-cost catalytic processes.
Angular‐momentum resolution in transitional‐mode state counting for loose transition states
Publisher: AIP Publishing
Date: 15-08-1992
DOI: 10.1063/1.463960
Abstract: The classical evaluation of the angular-momentum-resolved sum of states for the loosely hindered rotational degrees of freedom, i.e., the transitional modes, in loose transition states occurring in unimolecular dissociation, radical–radical recombination, ion–molecule, and other collision-complex-forming bimolecular reactions is considered. Exact analytic expressions are derived for the momentum-space volume available to the transitional modes at a given configuration q with energy E and total angular momentum vector J. The results are completely general with respect to the type of fragment rotors involved and their relative orientation within the loose transition state, and constitute a dramatically simplified technique for J-resolved classical state counting. The utility of the expressions lies in the fact that they obviate the necessity of numerical integration over the system’s momentum space, thus reducing substantially the computational effort involved in the exact evaluation of the transitional-mode sum of states. The present results verify expressions which were postulated to apply to arbitrary configurations in our earlier work.
Molecular dynamic simulations of interactions between LDH and NO3 - intercalates in aqueous solution
Publisher: Elsevier BV
Date: 05-2008
Enhanced Charge-Modulated Switchable CO2 Capture on Graphene-like BeN4 with Beryllium Vacancy
Publisher: American Chemical Society (ACS)
Date: 19-10-2022
Calculation of quantum resonance energies and lifetimes via quasi-minimum residual filter diagonalization
Publisher: Elsevier BV
Date: 1998
Calculation of the vibrational spectral density of NO2 via density correlation functions
Publisher: Elsevier BV
Date: 07-1997
Lanczos subspace filter diagonalization: Homogeneous recursive filtering and a low-storage method for the calculation of matrix elements
Publisher: Royal Society of Chemistry (RSC)
Date: 2001
DOI: 10.1039/B008991P
Time-dependent master equation simulation of complex elementary reactions in combustion: Application to the reaction of (CH2)-C-1 with C2H2 from 300-2000 K
Publisher: Royal Society of Chemistry (RSC)
Date: 07-09-2001
DOI: 10.1039/B102562G
Abstract: Computational simulations of the title reaction are presented, covering a temperature range from 300 to 2000 K. At lower temperatures we find that initial formation of the cyclopropene complex by addition of methylene to acetylene is irreversible, as is the stabilisation process via collisional energy transfer. Product branching between propargyl and the stable isomers is predicted at 300 K as a function of pressure for the first time. At intermediate temperatures (1200 K), complex temporal evolution involving multiple steady states begins to emerge. At high temperatures (2000 K) the timescale for subsequent unimolecular decay of thermalized intermediates begins to impinge on the timescale for reaction of methylene, such that the rate of formation of propargyl product does not admit a simple analysis in terms of a single time-independent rate constant until the methylene supply becomes depleted. Likewise, at the elevated temperatures the thermalized intermediates cannot be regarded as irreversible product channels. Our solution algorithm involves spectral propagation of a symmetrized version of the discretized master equation matrix, and is implemented in a high precision environment which makes hitherto unachievable low-temperature modelling a reality.
European Pulsar Timing Array limits on continuous gravitational waves from individual supermassive black hole binaries
Publisher: Oxford University Press (OUP)
Date: 19-11-2015
Dots versus antidots: Computational exploration of structure, magnetism, and half-metallicity in boron-nitride nanostructures
Publisher: American Chemical Society (ACS)
Date: 10-11-2009
DOI: 10.1021/JA9071942
Abstract: Triangle-shaped nanohole, nanodot, and lattice antidot structures in hexagonal boron-nitride (h-BN) monolayer sheets are characterized with density functional theory calculations utilizing the local spin density approximation. We find that such structures may exhibit very large magnetic moments and associated spin splitting. N-terminated nanodots and antidots show strong spin anisotropy around the Fermi level, that is, half-metallicity. While B-terminated nanodots are shown to lack magnetism due to edge reconstruction, B-terminated nanoholes can retain magnetic character due to the enhanced structural stability of the surrounding two-dimensional matrix. In spite of significant lattice contraction due to the presence of multiple holes, antidot super lattices are predicted to be stable, exhibiting lified magnetism as well as greatly enhanced half-metallicity. Collectively, the results indicate new opportunities for designing h-BN-based nanoscale devices with potential applications in the areas of spintronics, light emission, and photocatalysis.
Lattice distortion oriented angular self-assembly of monolayer titania sheets
Publisher: American Chemical Society (ACS)
Date: 23-12-2011
DOI: 10.1021/JA109314U
Abstract: Self-assembly of exfoliated monolayer titania sheets is investigated by detailed transmission electron microscopy and the force field calculations. It is demonstrated for the first time that slight but significant lattice distortions result in modified angular self-assembly of exfoliated monolayer Ti(0.87)O(2) sheets. These findings significantly broaden current knowledge of the self-assembly of exfoliated nanoscale layered sheets, which may render the potential manipulation of self-assembly of nanosheets.
trans–cis Isomerism and acylimine formation in DsRed chromophore models: Intrinsic rotation barriers
Publisher: Elsevier BV
Date: 07-2006
Quantum spin Hall effect and topological phase transition in two-dimensional square transition-metal dichalcogenides
Publisher: American Physical Society (APS)
Date: 25-08-2015
Kinetic modelling of molecular hydrogen transport in microporous carbon materials
Publisher: Royal Society of Chemistry (RSC)
Date: 2011
DOI: 10.1039/C0CP02235G
Abstract: The proposal of kinetic molecular sieving of hydrogen isotopes is explored by employing statistical rate theory methods to describe the kinetics of molecular hydrogen transport in model microporous carbon structures. A Lennard-Jones atom-atom interaction potential is utilized for the description of the interactions between H(2)/D(2) and the carbon framework, while the requisite partition functions describing the thermal flux of molecules through the transition state are calculated quantum mechanically in view of the low temperatures involved in the proposed kinetic molecular sieving application. Predicted kinetic isotope effects for initial passage from the gas phase into the first pore mouth are consistent with expectations from previous modeling studies, namely, that at sufficiently low temperatures and for sufficiently narrow pore mouths D(2) transport is dramatically favored over H(2). However, in contrast to expectations from previous modeling, the absence of any potential barrier along the minimum energy pathway from the gas phase into the first pore mouth yields a negative temperature dependence in the predicted absolute rate coefficients-implying a negative activation energy. In pursuit of the effective activation barrier, we find that the minimum potential in the cavity is significantly higher than in the pore mouth for nanotube-shaped models, throwing into question the common assumption that passage through the pore mouths should be the rate-determining step. Our results suggest a new mechanism that, depending on the size and shape of the cavity, the thermal activation barrier may lie in the cavity rather than at the pore mouth. As a consequence, design strategies for achieving quantum-mediated kinetic molecular sieving of H(2)/D(2) in a microporous membrane will need, at the very least, to take careful account of cavity shape and size in addition to pore-mouth size in order to ensure that the selective step, namely passage through the pore mouth, is also the rate determining step.
On the Location of Boron in SiO2‐Embedded Si Nanocrystals—An X‐ray Absorption Spectroscopy and Density Functional Theory Study
Publisher: Wiley
Date: 04-05-2021
Abstract: Doping of silicon nanostructures is crucial to understand their properties and to enhance their potential in various fields of application. Herein, SiO 2 ‐embedded Si nanocrystals (quantum dots) ≈3–6 nm in diameter are used as a model system to study the incorporation of B dopants by X‐ray absorption near‐edge spectroscopy (XANES). Such s les represent a model system for ultimately scaled, 3D‐confined Si nanovolumes. The analysis is complemented by real‐space density functional theory to calculate the 1 s (K shell) electron binding energies of B in 11 different, thermodynamically stable configurations of the Si/SiO x /SiO 2 system. Although no indications for a substitutional B‐acceptor configuration are found, the predominant O coordination of B indicates the preferred B incorporation into the SiO 2 matrix and near the Si‐nanocrystal/SiO 2 interface, which is inherently incompatible with charge carrier generation by dopants. It is concluded that B doping of ultrasmall Si nanostructures fails due to a lack of B incorporation onto Si lattice sites that cannot be overcome by increasing the B concentration. The inability to efficiently insert B into Si nanovolumes appears to be a boron‐specific fundamental obstacle for electronic doping (e.g., not observed for phosphorus) that adds to the established nanosize effects, namely, increased dopant activation and ionization energies.
Hybrid graphene/titania nanocomposite: Interface charge transfer, hole doping, and sensitization for visible light response
Publisher: American Chemical Society (ACS)
Date: 04-2011
DOI: 10.1021/JZ2002698
Abstract: We demonstrated for the first time by large-scale ab initio calculations that a graphene/titania interface in the ground electronic state forms a charge-transfer complex due to the large difference of work functions between graphene and titania, leading to substantial hole doping in graphene. Interestingly, electrons in the upper valence band can be directly excited from graphene to the conduction band, that is, the 3d orbitals of titania, under visible light irradiation. This should yield well-separated electron-hole pairs, with potentially high photocatalytic or photovoltaic performance in hybrid graphene and titania nanocomposites. Experimental wavelength-dependent photocurrent generation of the graphene/titania photoanode demonstrated noticeable visible light response and evidently verified our ab initio prediction.
Adsorption of Carbon Dioxide and Nitrogen on Single-Layer Aluminum Nitride Nanostructures Studied by Density Functional Theory
Publisher: American Chemical Society (ACS)
Date: 09-04-2010
DOI: 10.1021/JP911419K
Computer modeling study for intercalation of drug heparin into layered double hydroxide
Publisher: American Chemical Society (ACS)
Date: 07-2010
DOI: 10.1021/JP102724S
A PSEUDOSPECTRAL ALGORITHM FOR THE COMPUTATION OF TRANSITIONAL-MODE EIGENFUNCTIONS IN LOOSE TRANSITION-STATES
Publisher: Elsevier BV
Date: 09-1995
Removal of orthodontic bonding resin residues by CO2 laser radiation: Surface effects
Publisher: Mary Ann Liebert Inc
Date: 02-1999
Abstract: The purpose of this in vitro study was to evaluate the potential use of pulsed CO2 laser radiation to remove selectivity residues of orthodontic bonding resin that remain after debonding of fixed orthodontic appliances. Current techniques used for removal of orthodontic bonding resin after removal of fixed appliances include rotary instruments, debonding pliers, and ultrasonic scalers. These techniques, however, are time-consuming and inefficient, and may damage tooth enamel. A standardized cylinder of orthodontic bonding resin was bonded to the buccal surfaces of 100 extracted premolar teeth, which were then ided into 10 groups of 10 specimens each. In 9 groups, the resin was ablated using 1 of 9 different laser parameters, while in the remaining control group, the resin was removed with a slow speed tungsten carbide bur. Specimens were evaluated by light microscopy and scanning electron microscopy (SEM) to assess the amount of resin remaining and the extent of the damage to the underlying enamel. The 2 W/100 ms combination was optimal, with a high efficiency of resin removal and the least enamel damage. Higher laser powers increased the extent of enamel damage without enhancing resin removal. This laser technique appears promising, however, further studies of the extent of thermal changes at the level of the dental pulp are necessary to establish more fully the risk-benefit ratio.
Placing limits on the stochastic gravitational-wave background using European Pulsar Timing Array data
Publisher: Oxford University Press (OUP)
Date: 20-04-2011
Van der Waals-corrected density functional theory: benchmarking for hydrogen-nanotube and nanotube-nanotube interactions
Publisher: IOP Publishing
Date: 09-08-2005
DOI: 10.1088/0957-4484/16/10/024
Abstract: Density functional theory (DFT) is a powerful approach to electronic structure calculations in extended systems, but suffers currently from inadequate incorporation of long-range dispersion, or Van der Waals (VdW) interactions. VdW-corrected DFT is tested for interactions involving molecular hydrogen, graphite, single-walled carbon nanotubes (SWCNTs), and SWCNT bundles. The energy correction, based on an empirical London dispersion term with a d ing function at short range, allows a reasonable physisorption energy and equilibrium distance to be obtained for H(2) on a model graphite surface. The VdW-corrected DFT calculation for an (8, 8) nanotube bundle reproduces accurately the experimental lattice constant. For H(2) inside or outside an (8, 8) SWCNT, we find the binding energies are respectively higher and lower than that on a graphite surface, correctly predicting the well known curvature effect. We conclude that the VdW correction is a very effective method for implementing DFT calculations, allowing a reliable description of both short-range chemical bonding and long-range dispersive interactions. The method will find powerful applications in areas of SWCNT research where empirical potential functions either have not been developed, or do not capture the necessary range of both dispersion and bonding interactions.
Transition-state-theory calculations for reactions of O(P-3) with halogenated olefins
Publisher: Royal Society of Chemistry (RSC)
Date: 2004
DOI: 10.1039/B409689D
Interfacing BiVO4 with Reduced Graphene Oxide for Enhanced Photoactivity: A Tale of Facet Dependence of Electron Shuttling
Publisher: Wiley
Date: 21-07-2016
Abstract: Efficient interfacial charge transfer is essential in graphene-based semiconductors to realize their superior photoactivity. However, little is known about the factors (for ex le, semiconductor morphology) governing the charge interaction. Here, it is demonstrated that the electron transfer efficacy in reduced graphene oxide-bismuth oxide (RGO/BiVO
Extraordinary water adsorption characteristics of graphene oxide
Publisher: Royal Society of Chemistry (RSC)
Date: 2018
DOI: 10.1039/C8SC00545A
Abstract: The laminated structure of graphene oxide (GO) confers unique interactions with water molecules which may be utilised in a range of applications that require materials with tuneable hygroscopic properties.
Conductive Graphitic Carbon Nitride as an Ideal Material for Electrocatalytically Switchable CO2 Capture
Publisher: Springer Science and Business Media LLC
Date: 12-2015
DOI: 10.1038/SREP17636
Abstract: Good electrical conductivity and high electron mobility of the sorbent materials are prerequisite for electrocatalytically switchable CO 2 capture. However, no conductive and easily synthetic sorbent materials are available until now. Here, we examined the possibility of conductive graphitic carbon nitride (g-C 4 N 3 ) nanosheets as sorbent materials for electrocatalytically switchable CO 2 capture. Using first-principle calculations, we found that the adsorption energy of CO 2 molecules on g-C 4 N 3 nanosheets can be dramatically enhanced by injecting extra electrons into the adsorbent. At saturation CO 2 capture coverage, the negatively charged g-C 4 N 3 nanosheets achieve CO 2 capture capacities up to 73.9 × 10 13 cm −2 or 42.3 wt%. In contrast to other CO 2 capture approaches, the process of CO 2 capture/release occurs spontaneously without any energy barriers once extra electrons are introduced or removed and these processes can be simply controlled and reversed by switching on/off the charging voltage. In addition, these negatively charged g-C 4 N 3 nanosheets are highly selective for separating CO 2 from mixtures with CH 4 , H 2 and/or N 2 . These predictions may prove to be instrumental in searching for a new class of experimentally feasible high-capacity CO 2 capture materials with ideal thermodynamics and reversibility.
Charge modulation in graphitic carbon nitride as a switchable approach to high-capacity hydrogen storage
Publisher: Wiley
Date: 18-09-2015
Abstract: Electrical charging of graphitic carbon nitride nanosheets (g-C4 N3 and g-C3 N4 ) is proposed as a strategy for high-capacity and electrocatalytically switchable hydrogen storage. Using first-principle calculations, we found that the adsorption energy of H2 molecules on graphitic carbon nitride nanosheets is dramatically enhanced by injecting extra electrons into the adsorbent. At full hydrogen coverage, the negatively charged graphitic carbon nitride achieves storage capacities up to 6-7 wt %. In contrast to other hydrogen storage approaches, the storage/release occurs spontaneously once extra electrons are introduced or removed, and these processes can be simply controlled by switching on/off the charging voltage. Therefore, this approach promises both facile reversibility and tunable kinetics without the need of specific catalysts. Importantly, g-C4 N3 has good electrical conductivity and high electron mobility, which can be a very good candidate for electron injection/release. These predictions may prove to be instrumental in searching for a new class of high-capacity hydrogen storage materials.
Modelling carbon membranes for gas and isotope separation
Publisher: Royal Society of Chemistry (RSC)
Date: 2013
DOI: 10.1039/C3CP44414G
Abstract: Molecular modelling has become a useful and widely applied tool to investigate separation and diffusion behavior of gas molecules through nano-porous low dimensional carbon materials, including quasi-1D carbon nanotubes and 2D graphene-like carbon allotropes. These simulations provide detailed, molecular level information about the carbon framework structure as well as dynamics and mechanistic insights, i.e. size sieving, quantum sieving, and chemical affinity sieving. In this perspective, we revisit recent advances in this field and summarize separation mechanisms for multicomponent systems from kinetic and equilibrium molecular simulations, elucidating also anomalous diffusion effects induced by the confining pore structure and outlining perspectives for future directions in this field.
First-Principles Prediction of Metal-Free Magnetism and Intrinsic Half-Metallicity in Graphitic Carbon Nitride
Publisher: American Physical Society (APS)
Date: 11-05-2012
The role of Ti as a catalyst for the dissociation of hydrogen on a Mg(0001) surface
Publisher: American Chemical Society (ACS)
Date: 09-2005
DOI: 10.1021/JP052804C
Abstract: In this paper, the dissociative chemisorption of hydrogen on both pure and Ti-incorporated Mg(0001) surfaces are studied by ab initio density functional theory (DFT) calculations. The calculated dissociation barrier of hydrogen molecule on a pure Mg(0001) surface (1.05 eV) is in good agreement with comparable theoretical studies. For the Ti-incorporated Mg(0001) surface, the activated barrier decreases to 0.103 eV due to the strong interaction between the molecular orbital of hydrogen and the d metal state of Ti. This could explain the experimentally observed improvement in absorption kinetics of hydrogen when transition metals have been introduced into the magnesium materials.
Tuning conductivity and magnetism in isopolar oxide superlattices via compressive and tensile strain: A case study of SrVO 3 /SrMnO 3 and SrCrO 3 /SrMnO 3 heterostructure
Publisher: AIP Publishing
Date: 19-02-2016
DOI: 10.1063/1.4942214
Abstract: We demonstrate the role of compressive and tensile strain to effectively control the conductivity and magnetism in isopolar materials utilizing density functional theory. Using the ex les of superlattices containing transition metals with electronegativity differences such as SrVO3/SrMnO3 and SrCrO3/SrMnO3, our results show that the lattice strain can alter the apical oxygen shift at the interface of the transition metal layers, thus affecting the internal charge transfer process between d electrons. In addition, lattice compression and tensile strain can also modify the orbital occupancies of the manganite layers. As a result, various exotic effects can be realized in the SrMnO3 layer such as Mott insulator, quasi-two-dimensional conductivity, and long-range magnetism.
H-2 purification by functionalized graphdiyne - role of nitrogen doping
Publisher: Royal Society of Chemistry (RSC)
Date: 2015
DOI: 10.1039/C5TA01062D
Abstract: Nitrogen doping into graphdiyne leads to a reduced H 2 diffusion barrier and hence an enhanced hydrogen purification capability.
Formation of Single-Walled Carbon Nanotube via the Interaction of Graphene Nanoribbons: Ab Initio Density Functional Calculations
Publisher: American Chemical Society (ACS)
Date: 10-10-2007
DOI: 10.1021/NL071613D
Abstract: The interaction of bare graphene nanoribbons (GNRs) was investigated by ab initio density functional theory calculations with both the local density approximation (LDA) and the generalized gradient approximation (GGA). Remarkably, two bare 8-GNRs with zigzag-shaped edges are predicted to form an (8, 8) armchair single-wall carbon nanotube (SWCNT) without any obvious activation barrier. The formation of a (10, 0) zigzag SWCNT from two bare 10-GNRs with armchair-shaped edges has activation barriers of 0.23 and 0.61 eV for using the LDA and the revised PBE exchange correlation functional, respectively. Our results suggest a possible route to control the growth of specific types SWCNT via the interaction of GNRs.
Photodissociation of benzene under collision-free conditions: An ab initio /Rice–Ramsperger–Kassel–Marcus study
Publisher: AIP Publishing
Date: 30-03-2004
DOI: 10.1063/1.1676275
Abstract: The ab initio/Rice–Ramsperger–Kassel–Marcus (RRKM) approach has been applied to investigate the photodissociation mechanism of benzene at various wavelengths upon absorption of one or two UV photons followed by internal conversion into the ground electronic state. Reaction pathways leading to various decomposition products have been mapped out at the G2M level and then the RRKM and microcanonical variational transition state theories have been applied to compute rate constants for in idual reaction steps. Relative product yields (branching ratios) for C6H5+H, C6H4+H2, C4H4+C2H2, C4H2+C2H4, C3H3+C3H3, C5H3+CH3, and C4H3+C2H3 have been calculated subsequently using both numerical integration of kinetic master equations and the steady-state approach. The results show that upon absorption of a 248 nm photon dissociation is too slow to be observable in molecular beam experiments. In photodissociation at 193 nm, the dominant dissociation channel is H atom elimination (99.6%) and the minor reaction channel is H2 elimination, with the branching ratio of only 0.4%. The calculated lifetime of benzene at 193 nm is about 11 μs, in excellent agreement with the experimental value of 10 μs. At 157 nm, the H loss remains the dominant channel but its branching ratio decreases to 97.5%, while that for H2 elimination increases to 2.1%. The other channels leading to C3H3+C3H3, C5H3+CH3, C4H4+C2H2, and C4H3+C2H3 play insignificant role but might be observed. For photodissociation upon absorption of two UV photons occurring through the neutral “hot” benzene mechanism excluding dissociative ionization, we predict that the C6H5+H channel should be less dominant, while the contribution of C6H4+H2 and the C3H3+C3H3, CH3+C5H3, and C4H3+C2H3 radical channels should significantly increase.
Calculation of bound and resonance states of HO2 for nonzero total angular momentum
Publisher: AIP Publishing
Date: 20-05-2003
DOI: 10.1063/1.1572132
Abstract: Bound and resonance states of HO2 have been calculated quantum mechanically by the Lanczos homogeneous filter diagonalization method [Zhang and Smith, Phys. Chem. Chem. Phys. 3, 2282 (2001) J. Chem. Phys. 115, 5751 (2001)] for nonzero total angular momentum J=1,2,3. For lower bound states, agreement between the results in this paper and previous work is quite satisfactory while for high lying bound states and resonances these are the first reported results. A helicity quantum number Ω assignment (within the helicity conserving approximation) is performed and the results indicate that for lower bound states it is possible to assign the Ω quantum numbers unambiguously, but for resonances it is impossible to assign the Ω helicity quantum numbers due to strong mixing. In fact, for the high-lying bound states, the mixing has already appeared. These results indicate that the helicity conserving approximation is not good for the resonance state calculations and exact quantum calculations are needed to accurately describe the reaction dynamics for HO2 system. Analysis of the resonance widths shows that most of the resonances are overlapping and the interferences between them lead to large fluctuations from one resonance to another. In accord with the conclusions from earlier J=0 calculations, this indicates that the dissociation of HO2 is essentially irregular.
Theoretical study of the reaction CH(X-2 Pi)+NO(X-2 Pi). 3. Determination of the branching ratios
Publisher: American Chemical Society (ACS)
Date: 22-04-1998
DOI: 10.1021/JP980159M
A Lanczos-powered implementation of the Faber polynomial quantum time propagator for reaction probabilities
Publisher: Elsevier BV
Date: 04-2004
Formation energies of low-indexed surfaces of tin dioxide terminated by nonmetals
Publisher: Elsevier BV
Date: 05-2010
Design guidelines for transition metals as interstitial emitters in silicon nanocrystals to tune photoluminescence properties: zinc as biocompatible example
Publisher: Royal Society of Chemistry (RSC)
Date: 2020
DOI: 10.1039/D0NR05156J
Abstract: General photoluminescence design rules for interstitial transition-metal-doped silicon nanocrystals are derived Zn shows excellent properties for medical imaging and plasmonic microwave excitation to exactly eliminate marked cells.
ENTROPY BARRIERS TO PROTON-TRANSFER
Publisher: American Chemical Society (ACS)
Date: 1991
DOI: 10.1021/JA00003A020
Half metallicity in a zigzag double-walled nanotube nanodot: An ab initio prediction
Publisher: Elsevier BV
Date: 2009
Quantum Chemical Characterization of Low-Lying Excited States of an Aryl Peroxycarbonate: Mechanistic Implications for Photodissociation
Publisher: American Chemical Society (ACS)
Date: 04-03-2010
DOI: 10.1021/JP9029166
Abstract: Recent experiments have revealed the existence of an excited state dissociative mechanism for certain peroxycarbonates, with the demonstration that the lifetime of the excited state matches the picosecond time scale for appearance of nascent carbon dioxide product. The data infer that the photoreaction proceeds via an effectively concerted three-body dissociation within the lifetime of the singlet excited state. Many other arylperoxides decay sequentially via [(aryloxy)carbonyl]oxy radical intermediates on nanosecond-microsecond time scales. Uncertainty as to the lifetime of the excited state relates to the character and the relative energetic ordering of states of the parent molecule, since the spectra and photochemistry imply that low-lying states may exist on each of the aryl, carbonate, and peroxide chemical functionalities. We employ many-body electronic structure calculations to determine the energies and characters of the low-lying valence states of a minimal aryl peroxycarbonate model germane to the above-mentioned experiments, methyl phenyl peroxycarbonate (MPC). Our results indicate that the lowest-lying state is an intrinsically nondissociative aryl pipi* excited state. We identify additional low-lying states that are expected to be dissociative in nature and propose that the time scales observed for the dissociation reaction may correspond to the time scale for transfer of excited state population to these states.
The Mechanism of Cyclization in Chromophore Maturation of Green Fluorescent Protein: A Theoretical Study
Publisher: American Chemical Society (ACS)
Date: 07-2010
DOI: 10.1021/JP1039817
Abstract: An intriguing aspect of the green fluorescent protein (GFP) is the autocatalytic post-translational modification that results in the formation of its chromophore. Numerous experimental and theoretical studies indicate that cyclization is the first and the most important step in the maturation process. In this work, two proposed mechanisms for the cyclization were investigated by using the hybrid density functional theory method B3LYP. Cluster models corresponding to the two mechanisms proposed by Wachter et al. [J. Biol. Chem. 2005, 280, 26248-26255] are constructed on the basis of the X-ray crystal structure (PDB entry 2AWJ) and corresponding reaction path potential energy profiles for the two cyclization mechanisms are presented. Our results suggest that the backbone condensation initiated by deprotonation of the Gly67 amide nitrogen is easier than deprotonation of the Tyr66 alpha-carbon. Moreover, Arg96 fulfills the role of stabilizing the enolate moiety, and Glu222 plays the role of a general base. The formation of the cyclized product is found to be 16.0 and 18.6 kcal/mol endothermic with respect to the two models, which is in agreement with experimental observation.
The location of Ti atom in sodium alanate: an ab initio spin-polarised study
Publisher: Inderscience Publishers
Date: 2007
Structural and Relaxation Effects in Proton Wire Energetics: Model Studies of the Green Fluorescent Protein Photocycle
Publisher: CSIRO Publishing
Date: 2010
DOI: 10.1071/CH09509
Abstract: We present the results of a systematic series of constrained minimum energy pathway calculations on ground state potential energy surfaces, for a cluster model of the proton chain transfer that mediates the photocycle of the green fluorescent protein, as well as for a model including the solvated protein environment. The calculations vary in terms of the types of modes that are assumed to be capable of relaxing in concert with the movement of the protons and the results demonstrate that the nature and extent of dynamical relaxation has a substantive impact on the activation energy for the proton transfer. We discuss the implications of this in terms of currently available dynamical models and chemical rate theories that might be brought to bear on the kinetics of this important ex le of proton chain transfer in a biological system.
Ab initio modelling of basal plane oxidation of graphenes and implications for modelling char combustion
Publisher: Elsevier BV
Date: 2002
Subspace wavepacket evolution with Newton polynomials
Publisher: Elsevier BV
Date: 03-2001
Enhanced stability and stacking dependent magnetic/electronic properties of 2D monolayer FeTiO3 on a Ti2CO2 substrate
Publisher: Royal Society of Chemistry (RSC)
Date: 2019
DOI: 10.1039/C9TC04979G
Abstract: With large magnetic moments, complete spin-polarization, high T C , and tunable magnetism characters, 2D FeTiO 3 /Ti 2 CO 2 is proposed as an ideal material for high-performance spintronics.
Using social network analysis to understand multisectoral governance in district-level tobacco control programme implementation in India
Publisher: BMJ
Date: 2022
DOI: 10.1136/BMJGH-2021-006471
Abstract: Interest in multisectoral policies has increased, particularly in the context of low-income and middle-income countries and efforts towards Sustainable Development Goals, with greater attention to understand effective strategies for implementation and governance. The study aimed to explore and map the composition and structure of a multisectoral initiative in tobacco control, identifying key factors engaged in policy implementation and their patterns of relationships in local-level networks in two districts in the state of Karnataka, India. Social network analysis (SNA) was used to examine the structure of two district tobacco control networks with differences in compliance with the India’s national tobacco control law. The survey was administered to 108 respondents (n=51 and 57) in two districts, producing three distinct network maps about interaction, information-seeking and decision-making patterns within each district. The network measures of centrality, density, reciprocity, centralisation and E-I index were used to understand and compare across the two districts. Members from the department of health, especially those in the District Tobacco Control Cell, were the most frequently consulted actors for information as they led district-level networks. The most common departments engaged beyond health were education, police and municipal. District 1’s network displayed high centralisation, with a district nodal officer who exercised a central role with the highest in-degree centrality. The district also exhibited greater density and reciprocity. District 2 showed a more dispersed pattern, where subdistrict health managers had higher betweenness centrality and acted as brokers in the network. Collaboration and cooperation among sectors and departments are essential components of multisectoral policy. SNA provides a mechanism to uncover the nature of relationships and key actors in collaborative dynamics. It can be used as a visual learning tool for policy planners and implementers to understand the structure of actual implementation and concentrate their efforts to improve and enhance collaboration.
Hydrogen spillover mechanism on a Pd-doped Mg surface as revealed by ab initio density functional calculation
Publisher: American Chemical Society (ACS)
Date: 31-07-2007
DOI: 10.1021/JA0722776
Abstract: The hydrogenation kinetics of Mg is slow, impeding its application for mobile hydrogen storage. We demonstrate by ab initio density functional theory (DFT) calculations that the reaction path can be greatly modified by adding transition metal catalysts. Contrasting with Ti doping, a Pd dopant will result in a very small activation barrier for both dissociation of molecular hydrogen and diffusion of atomic H on the Mg surface. This new computational finding supports-for the first time by ab initio simulation-the proposed hydrogen spillover mechanism for rationalizing experimentally observed fast hydrogenation kinetics for Pd-capped Mg materials.
Dynamical Interactions of 5-Fluorouracil Drug with Dendritic Peptide Vectors
Publisher: American Chemical Society (ACS)
Date: 20-06-2016
Abstract: Molecular dynamics simulations are utilized to investigate the interactions between the skin cancer drug 5-fluorouracil (5FU) and peptide-based dendritic carrier systems. We find that these drug-carrier interactions do not conform to the traditional picture of long-time retention of the drug within a hydrophobic core of the dendrimer carrier. Rather, 5FU, which is moderately soluble in its own right, experiences weak, transient chattering interactions all over the dendrimer, mediated through multiple short-lived hydrogen bonding and close contact events. We find that charge on the periphery of the dendrimer actually has a negative effect on the frequency of drug-carrier interactions due to a counterion screening effect that has not previously been observed. However, charge is nevertheless an important feature since neutral dendrimers are shown to have a significant mutual attraction that can lead to clustering or agglomeration. This clustering is prevented due to charge repulsion for the titrated dendrimers, such that they remain independent in solution.
First principle studies of zigzag AlN nanoribbon
Publisher: Elsevier BV
Date: 02-2009
The mechanism of dehydration in chromophore maturation of wild-type green fluorescent protein: A theoretical study
Publisher: Elsevier BV
Date: 07-2015
P-Doped Graphene/Graphitic Carbon Nitride Hybrid Electrocatalysts: Unraveling Charge Transfer Mechanisms for Enhanced Hydrogen Evolution Reaction Performance
Publisher: American Chemical Society (ACS)
Date: 21-09-2016
ANGULAR-MOMENTUM CONSERVATION IN UNIMOLECULAR AND RECOMBINATION REACTIONS
Publisher: Wiley
Date: 04-1988
Huge Lithium Storage in 2D Bilayer Structures with Point Defects
Publisher: American Chemical Society (ACS)
Date: 21-10-2021
In Operando Self-Healing of Perovskite Electrocatalysts: A Case Study of SrCoO3 for the Oxygen Evolution Reaction
Publisher: Wiley
Date: 24-01-2017
Flux Factors in Variational Transition-State Theory
Publisher: American Chemical Society (ACS)
Date: 06-1994
DOI: 10.1021/J100077A013
State-to-state reactive differential cross sections for the H + H2 -> H2 + H reaction on five different potential energy surfaces employing a new quantum wavepacket computer code: DIFFREALWAVE
Publisher: AIP Publishing
Date: 23-10-2006
DOI: 10.1063/1.2358350
Abstract: State-to-state differential cross sections have been calculated for the hydrogen exchange reaction, H+H2→H2+H, using five different high quality potential energy surfaces with the objective of examining the sensitivity of these detailed cross sections to the underlying potential energy surfaces. The calculations were performed using a new parallel computer code, DIFFREALWAVE. The code is based on the real wavepacket approach of Gray and Balint-Kurti [J. Chem. Phys. 108, 950 (1998)]. The calculations are parallelized over the helicity quantum number Ω′ (i.e., the quantum number for the body-fixed z component of the total angular momentum) and wavepackets for each J,Ω′ set are assigned to different processors, similar in spirit to the Coriolis-coupled processors approach of Goldfield and Gray [Comput. Phys. Commun. 84, 1 (1996)]. Calculations for J=0–24 have been performed to obtain converged state-to-state differential cross sections in the energy range from 0.4to1.2eV. The calculations employ five different potential energy surfaces, the BKMP2 surface and a hierarchical family of four new ab initio surfaces [S. L. Mielke, et al., J. Chem. Phys. 116, 4142 (2002)]. This family of four surfaces has been calculated using three different hierarchical sets of basis functions and also an extrapolation to the complete basis set limit, the so called CCI surface. The CCI surface is the most accurate surface for the H3 system reported to date. Our calculations of differential cross sections are the first to be reported for the A2, A3, A4, and CCI surfaces. They show that there are some small differences in the cross sections obtained from the five different surfaces, particularly at higher energies. The calculations also show that the BKMP2 performs well and gives cross sections in very good agreement with the results from the CCI surface, displaying only small ergences at higher energies.
Tungsten Oxide/Carbide Surface Heterojunction Catalyst with High Hydrogen Evolution Activity
Publisher: American Chemical Society (ACS)
Date: 23-10-2020
Electronic Functionality in Graphene-Based Nanoarchitectures: Discovery and Design via First-Principles Modeling
Publisher: American Chemical Society (ACS)
Date: 23-12-2011
DOI: 10.1021/JZ101347A
Abstract: Graphene has promised many novel applications in nanoscale electronics and sustainable energy due to its novel electronic properties. Computational exploration of electronic functionality and how it varies with architecture and doping presently runs ahead of experimental synthesis yet provides insights into types of structures that may prove profitable for targeted experimental synthesis and characterization. We present here a summary of our understanding on the important aspects of dimension, band gap, defect, and interfacial engineering of graphene based on state-of-the-art ab initio approaches. Some most recent experimental achievements relevant for future theoretical exploration are also covered.
Surface Reconstruction of Ultrathin Palladium Nanosheets during Electrocatalytic CO2 Reduction
Publisher: Wiley
Date: 17-09-2020
The isotopic effects of deuteration on optoelectronic properties of conducting polymers
Publisher: Springer Science and Business Media LLC
Date: 24-01-2014
DOI: 10.1038/NCOMMS4180
Abstract: The attractive optoelectronic properties of conducting polymers depend sensitively upon intra- and inter-polymer chain interactions, and therefore new methods to manipulate these interactions are continually being pursued. Here, we report a study of the isotopic effects of deuterium substitution on the structure, morphology and optoelectronic properties of regioregular poly(3-hexylthiophene)s with an approach that combines the synthesis of deuterated materials, optoelectronic properties measurements, theoretical simulation and neutron scattering. Selective substitutions of deuterium on the backbone or side-chains of poly(3-hexylthiophene)s result in distinct optoelectronic responses in poly(3-hexylthiophene)/[6,6]-phenyl-C61-butyric acid methyl ester (PCBM) photovoltaics. Specifically, the weak non-covalent intermolecular interactions induced by the main-chain deuteration are shown to change the film crystallinity and morphology of the active layer, consequently reducing the short-circuit current. However, side-chain deuteration does not significantly modify the film morphology but causes a decreased electronic coupling, the formation of a charge transfer state, and increased electron-phonon coupling, leading to a remarkable reduction in the open circuit voltage.
Strong Interaction between Gold and Anatase TiO2(001) Predicted by First Principle Studies
Publisher: American Chemical Society (ACS)
Date: 25-01-2012
DOI: 10.1021/JP208948X
Sulfur‐Dopant‐Promoted Electroreduction of CO2 over Coordinatively Unsaturated Ni‐N2 Moieties
Publisher: Wiley
Date: 24-09-2021
Abstract: Atomically dispersed nickel–nitrogen–carbon (Ni‐N‐C) moieties are promising for efficient electrochemical CO 2 ‐to‐CO conversion. To improve the intrinsic electrocatalytic activity, it is essential but challenging to steer the coordination environment of Ni centers for promoting the CO formation kinetics. Here, we introduce alien sulfur atoms to tune the local electronic density of unsaturated NiN 2 species. A coordinated structure evolution is detected and S vacancies are generated at high overpotentials, as confirmed by X‐ray absorption spectroscopy. The sulfur dopants enhance CO selectivity and activity over normal unsaturated NiN 2 structure, reaching a high CO Faradaic efficiency of 97 % and a large CO current density of 40.3 mA cm −2 in a H‐cell at −0.8 V and −0.9 V (vs. RHE), respectively. DFT calculations reveal both doped S atoms and evolved S vacancies in the NiN 2 coordination environment contribute to the reduced energy barriers for CO 2 electroreduction to CO.
Role of charge in destabilizingAlH 4
Publisher: American Physical Society (APS)
Date: 08-11-2006
Determination of chromophore charge states in the low pH color transition of the fluorescent protein Rtms5H146S via time-dependent DFT
Publisher: Elsevier BV
Date: 03-2006
Atomically Dispersed Indium Sites for Selective CO2 Electroreduction to Formic Acid
Publisher: American Chemical Society (ACS)
Date: 15-02-2021
Unraveling Photocatalytic Mechanism and Selectivity in PET-RAFT Polymerization
Publisher: Wiley
Date: 15-04-2019
Interaction of Water with the Fluorine-Covered Anatase TiO2 (001) Surface
Publisher: American Chemical Society (ACS)
Date: 05-08-2011
DOI: 10.1021/JP204900G
Trace doping of early transition metal enabled efficient and durable oxygen reduction catalysis on Pt-based ultrathin nanowires
Publisher: Elsevier BV
Date: 04-2022
Modulation Doping of Silicon using Aluminium-induced Acceptor States in Silicon Dioxide
Publisher: Springer Science and Business Media LLC
Date: 20-04-2017
DOI: 10.1038/SREP46703
Abstract: All electronic, optoelectronic or photovoltaic applications of silicon depend on controlling majority charge carriers via doping with impurity atoms. Nanoscale silicon is omnipresent in fundamental research (quantum dots, nanowires) but also approached in future technology nodes of the microelectronics industry. In general, silicon nanovolumes, irrespective of their intended purpose, suffer from effects that impede conventional doping due to fundamental physical principles such as out-diffusion, statistics of small numbers, quantum- or dielectric confinement. In analogy to the concept of modulation doping, originally invented for III-V semiconductors, we demonstrate a heterostructure modulation doping method for silicon. Our approach utilizes a specific acceptor state of aluminium atoms in silicon dioxide to generate holes as majority carriers in adjacent silicon. By relocating the dopants from silicon to silicon dioxide, Si nanoscale doping problems are circumvented. In addition, the concept of aluminium-induced acceptor states for passivating hole selective tunnelling contacts as required for high-efficiency photovoltaics is presented and corroborated by first carrier lifetime and tunnelling current measurements.
Anisotropic Ripple Deformation in Phosphorene
Publisher: American Chemical Society (ACS)
Date: 09-04-2015
DOI: 10.1021/ACS.JPCLETT.5B00522
Abstract: Two-dimensional materials tend to become crumpled according to the Mermin-Wagner theorem, and the resulting ripple deformation may significantly influence electronic properties as observed in graphene and MoS2. Here, we unveil by first-principles calculations a new, highly anisotropic ripple pattern in phosphorene, a monolayer black phosphorus, where compression-induced ripple deformation occurs only along the zigzag direction in the strain range up to 10%, but not the armchair direction. This direction-selective ripple deformation mode in phosphorene stems from its puckered structure with coupled hinge-like bonding configurations and the resulting anisotropic Poisson ratio. We also construct an analytical model using classical elasticity theory for ripple deformation in phosphorene under arbitrary strain. The present results offer new insights into the mechanisms governing the structural and electronic properties of phosphorene crucial to its device applications.
Selecting Methods to Solve Multi-Well Master Equations
Publisher: World Scientific Pub Co Pte Lt
Date: 06-2003
DOI: 10.1142/S0219633603000483
Abstract: There are several competing methods commonly used to solve energy grained master equations describing gas-phase reactive systems. When it comes to selecting an appropriate method for any particular problem, there is little guidance in the literature. In this paper we directly compare several variants of spectral and numerical integration methods from the point of view of computer time required to calculate the solution and the range of temperature and pressure conditions under which the methods are successful. The test case used in the comparison is an important reaction in combustion chemistry and incorporates reversible and irreversible bimolecular reaction steps as well as isomerizations between multiple unimolecular species. While the numerical integration of the ODE with a stiff ODE integrator is not the fastest method overall, it is the fastest method applicable to all conditions.
A Janus MoSSe monolayer: a superior and strain-sensitive gas sensing material
Publisher: Royal Society of Chemistry (RSC)
Date: 2019
DOI: 10.1039/C8TA08407F
Abstract: Due to the presence of intrinsic polarization, Janus MoSSe is proposed as an ideal material for controllable ultrahigh-sensitive sensors.
Flexibility of Short-Strand RNA in Aqueous Solution as Revealed by Molecular Dynamics Simulation: Are A-RNA and A´-RNA Distinct Conformational Structures?
Publisher: CSIRO Publishing
Date: 2009
DOI: 10.1071/CH09090
Abstract: We use molecular dynamics simulations to compare the conformational structure and dynamics of a 21-base pair RNA sequence initially constructed according to the canonical A-RNA and A′-RNA forms in the presence of counterions and explicit water. Our study aims to add a dynamical perspective to the solid-state structural information that has been derived from X-ray data for these two characteristic forms of RNA. Analysis of the three main structural descriptors commonly used to differentiate between the two forms of RNA – namely major groove width, inclination and the number of base pairs in a helical twist – over a 30 ns simulation period reveals a flexible structure in aqueous solution with fluctuations in the values of these structural parameters encompassing the range between the two crystal forms and more. This provides evidence to suggest that the identification of distinct A-RNA and A′-RNA structures, while relevant in the crystalline form, may not be generally relevant in the context of RNA in the aqueous phase. The apparent structural flexibility observed in our simulations is likely to bear ramifications for the interactions of RNA with biological molecules (e.g. proteins) and non-biological molecules (e.g. non-viral gene delivery vectors).
Exceptional Optoelectronic Properties of Hydrogenated Bilayer Silicene
Publisher: American Physical Society (APS)
Date: 19-05-2014
Unusual synergistic effect in layered Ruddlesden−Popper oxide enables ultrafast hydrogen evolution
Publisher: Springer Science and Business Media LLC
Date: 11-01-2019
DOI: 10.1038/S41467-018-08117-6
Abstract: Efficient electrocatalysts for hydrogen evolution reaction are key to realize clean hydrogen production through water splitting. As an important family of functional materials, transition metal oxides are generally believed inactive towards hydrogen evolution reaction, although many of them show high activity for oxygen evolution reaction. Here we report the remarkable electrocatalytic activity for hydrogen evolution reaction of a layered metal oxide, Ruddlesden−Popper-type Sr 2 RuO 4 with alternative perovskite layer and rock-salt SrO layer, in an alkaline solution, which is comparable to those of the best electrocatalysts ever reported. By theoretical calculations, such excellent activity is attributed mainly to an unusual synergistic effect in the layered structure, whereby the (001) SrO-terminated surface cleaved in rock-salt layer facilitates a barrier-free water dissociation while the active apical oxygen site in perovskite layer promotes favorable hydrogen adsorption and evolution. Moreover, the activity of such layered oxide can be further improved by electrochemistry-induced activation.
A real symmetric Lanczos subspace implementation of quantum scattering using boundary inhomogeneities
Publisher: Elsevier BV
Date: 12-2002
The origin of low workfunctions in OH terminated MXenes
Publisher: Royal Society of Chemistry (RSC)
Date: 2017
DOI: 10.1039/C7NR01601H
Abstract: The workfunction is an important parameter that governs several electronic phenomena occurring at the surfaces and interfaces of materials. Here, we study MXenes, which are two dimensional metal carbides and nitrides. The workfunction is strongly dependent on the terminating functional groups which induce surface dipoles and Fermi level shifts. Here, we establish a correlation between the workfunction and the adsorbate's 2p band centres. Focusing on the OH terminated MXenes which have intrinsically low workfunctions, we show that a rigid relation between the 2p band centres and workfunctions exists which resembles a volcano plot. This imposes a limit on the lowest possible workfunctions of ∼1.2 eV and sets an optimum value of the 2p band centres at which this low workfunction can occur which we determined to be ∼-5.45 eV relative to the Fermi level. We demonstrate that neither strain modulation nor doping can achieve workfunctions lower than this.
Symmetry contaminations in reactive scattering through long-lived collision complexes
Publisher: Elsevier BV
Date: 2005
Gas-Permeable Extended Wear and Complications
Publisher: Elsevier
Date: 2006
Single Mo1(Cr1) Atom on Nitrogen-Doped Graphene Enables Highly Selective Electroreduction of Nitrogen into Ammonia
Publisher: American Chemical Society (ACS)
Date: 19-03-2019
General discussion
Publisher: Elsevier BV
Date: 07-2006
Turning Low-Nanoscale Intrinsic Silicon Highly Electron-Conductive by SiO2 Coating
Publisher: American Chemical Society (ACS)
Date: 20-04-2021
Bond Selection in the Photoisomerization Reaction of Anionic Green Fluorescent Protein and Kindling Fluorescent Protein Chromophore Models
Publisher: American Chemical Society (ACS)
Date: 14-06-2008
DOI: 10.1021/JA078193E
Abstract: The chromophores of the most widely known fluorescent proteins (FPs) are derivatives of a core p-hydroxybenzylidene-imidazolinon-5-one (HBI) motif, which usually occurs as a phenolate anion. Double bond photoisomerization of the exocyclic bridge of HBI is widely held to be an important internal conversion mechanism for FP chromophores. Herein we describe the ground and excited-state electronic structures and potential energy surfaces of two model chromophores: 4- p-hydroxybenzylidiene-1,2-dimethyl-imidazolin-5-one anion (HBDI), representing green FPs (GFPs), and 2-acetyl-4-hydroxybenylidene-1-methyl-imidazolin-5-one anion (AHBMI), representing kindling FPs (KFPs). These chromophores differ by a single substitution, but we observe qualitative differences in the potential energy surfaces which indicate inversion of bond selection in the photoisomerization reaction. Bond selection is also modulated by whether the reaction proceeds from a Z or an E conformation. These configurations correspond to fluorescent and nonfluorescent states of structurally characterized FPs, including some which can be reversibly switched by specific illumination regimes. We explain the difference in bond selectivity via substituent stabilization effects on a common set of charge-localized chemical structures. Different combinations of these structures give rise to both optically active (planar) and twisted intramolecular charge-transfer (TICT) states of the molecules. We offer a prediction of the gas-phase absorption of AHBMI, which has not yet been measured. We offer a hypothesis to explain the unusual fluorescence of AHBMI in DMF solution, as well as an experimental proposal to test our hypothesis.
Fast, scalable master equation solution algorithms. III. Direct time propagation accelerated by a diffusion approximation preconditioned iterative solver
Publisher: AIP Publishing
Date: 18-12-2003
DOI: 10.1063/1.1628213
Abstract: In this paper we propose a novel fast and linearly scalable method for solving master equations arising in the context of gas-phase reactive systems, based on an existent stiff ordinary differential equation integrator. The required solution of a linear system involving the Jacobian matrix is achieved using the GMRES iteration preconditioned using the diffusion approximation to the master equation. In this way we avoid the cubic scaling of traditional master equation solution methods and maintain the low temperature robustness of numerical integration. The method is tested using a master equation modelling the formation of propargyl from the reaction of singlet methylene with acetylene, proceeding through long lived isomerizing intermediates.
Fast, scalable master equation solution algorithms. IV. Lanczos iteration with diffusion approximation preconditioned iterative inversion
Publisher: AIP Publishing
Date: 18-12-2003
DOI: 10.1063/1.1628214
Abstract: In this paper we propose a second linearly scalable method for solving large master equations arising in the context of gas-phase reactive systems. The new method is based on the well-known shift-invert Lanczos iteration using the GMRES iteration preconditioned using the diffusion approximation to the master equation to provide the inverse of the master equation matrix. In this way we avoid the cubic scaling of traditional master equation solution methods while maintaining the speed of a partial spectral decomposition. The method is tested using a master equation modeling the formation of propargyl from the reaction of singlet methylene with acetylene, proceeding through long-lived isomerizing intermediates.
Light-Induced Synergistic Multidefect Sites on TiO2/SiO2 Composites for Catalytic Dehydrogenation
Publisher: American Chemical Society (ACS)
Date: 12-02-2019
Electrocatalytically Switchable CO2 Capture: First Principle Computational Exploration of Carbon Nanotubes with Pyridinic Nitrogen
Publisher: Wiley
Date: 02-2014
Abstract: Carbon nanotubes with specific nitrogen doping are proposed for controllable, highly selective, and reversible CO2 capture. Using density functional theory incorporating long-range dispersion corrections, we investigated the adsorption behavior of CO2 on (7,7) single-walled carbon nanotubes (CNTs) with several nitrogen doping configurations and varying charge states. Pyridinic-nitrogen incorporation in CNTs is found to induce an increasing CO2 adsorption strength with electron injecting, leading to a highly selective CO2 adsorption in comparison with N2 . This functionality could induce intrinsically reversible CO2 adsorption as capture/release can be controlled by switching the charge carrying state of the system on/off. This phenomenon is verified for a number of different models and theoretical methods, with clear ramifications for the possibility of implementation with a broader class of graphene-based materials. A scheme for the implementation of this remarkable reversible electrocatalytic CO2 -capture phenomenon is considered.
Absorption and Photoluminescence of Silicon Nanocrystals Investigated by Excited State DFT: Role of Embedding Dielectric and Defects
Publisher: Wiley
Date: 16-03-2022
Abstract: Absorption and photoluminescence (PL) properties of silicon (Si) nanocrystals (NCs) covered with silicon dioxide () are fairly well unraveled corresponding information for silicon nitride () coverage is scarce. We elucidate important optical and electronic features depending on the embedding dielectric and interface defect (dangling bond, DB) properties. Using density functional theory (DFT) and time‐dependent (TD‐) DFT for ground state (GS) and excited state (ES) properties, respectively, we compute fully ‐ and OH‐covered NCs of 11–26 Å size, enabling comparisons with experimental data. Our non‐radiative Shockley‐Read‐Hall (SRH) recombination model of DBs at NC/dielectric interfaces demonstrates that SRH recombination is substantially higher for ‐covered NCs. An ensemble TD‐DFT calculation of the eight lowest fundamental transitions accurately describes the absorption edge. Exciton binding energies are significantly smaller in ‐ versus ‐covered NCs due to the delocalizing versus self‐localizing impact of the dielectric onto the exciton. We find higher optical absorption rates for ‐embedded NCs versus ‐embedded NCs. However, SRH interface recombination renders the PL of ‐embedded NCs inferior to their ‐embedded counterparts. Finally, we explain a discrepancy in PL gaps of free‐standing oxidized versus ‐embedded NCs by considering adequate phononic boundary conditions.
Calculation of absolute spectral densities via stochastic estimators of tr{δ(E - Ĥ)}
Publisher: Elsevier BV
Date: 10-1997
Convergent Proton-Transfer Photocycles Violate Mirror-Image Symmetry in a Key Melanin Monomer
Publisher: American Chemical Society (ACS)
Date: 05-2007
DOI: 10.1021/JA069280U
QM/MM studies of structural and energetic properties of the far-red fluorescent protein HcRed
Publisher: Royal Society of Chemistry (RSC)
Date: 2010
DOI: 10.1039/B918523B
Abstract: The far-red fluorescent protein HcRed was investigated using molecular dynamics (MD) and combined quantum mechanics/molecular mechanics (QM/MM) calculations. Three models of HcRed (anionic chromophore) were considered, differing in the protonation states of nearby Glu residues (A: Glu214 and Glu146 both protonated B: Glu214 protonated and Glu146 deprotonated C: Glu214 and Glu146 both deprotonated). SCC-DFTB/MM MD simulations of model B yield good agreement with the available crystallographic data at ambient pH. Bond lengths in the QM region are well reproduced, with a root mean square (rms) deviation between experimental and average MD data of 0.079 A the chromophore is almost co-planar, which is consistent with experimental observation and the five hydrogen bonds involving the chromophore are conserved. QM/MM geometry optimizations were performed on representative snapshot structures from the MD simulations for each model. They confirm the structural features observed in the MD simulations. According to the DFT(B3LYP)/MM results, the cis-conformation of the chromophore is more stable than the trans-form by 9.1-12.9 kcal mol(-1) in model B, and by 12.4-19.9 kcal mol(-1) in model C, consistent with the experimental preference for the cis-isomer. However, in model A when both Glu214 and Glu146 are protonated, the stability is inverted with the trans-form being favored. The different protonation states of the titratable active-site residues Glu214 and Glu146 thus critically influence the manner in which the relative stability and degree of planarity of the cis- and trans-conformers vary with pH. Coupled with the known correlation of chromophore conformation with fluorescence efficiency, this work provides a detailed structural basis for the observed phenomenon that red fluorescent proteins such as HcRed, mKate and Rtms5 show bright fluorescence at high pH.
Oxygen vacancy induced structural variations of exfoliated monolayer MnO2 sheets
Publisher: American Physical Society (APS)
Date: 03-02-2010
Metallic and Carbon Nanotube-Catalyzed Coupling of Hydrogenation in Magnesium
Publisher: American Chemical Society (ACS)
Date: 23-11-2007
DOI: 10.1021/JA0751431
Abstract: Synergistic effect of metallic couple and carbon nanotubes on Mg results in an ultrafast kinetics of hydrogenation that overcome a critical barrier of practical use of Mg as hydrogen storage materials. The ultrafast kinetics is attributed to the metal-H atomic interaction at the Mg surface and in the bulk (energy for bonding and releasing) and atomic hydrogen diffusion along the grain boundaries (aggregation of carbon nanotubes) and inside the grains. Hence, a hydrogenation mechanism is presented.
Non-equilibrium dynamics, materials and structures for hot carrier solar cells: a detailed review
Publisher: IOP Publishing
Date: 17-06-2020
State-to-state reaction probabilities for the H + O2 (v,j) -> O + OH (v′, j′) reaction on three potential energy surfaces
Publisher: AIP Publishing
Date: 14-08-2007
DOI: 10.1063/1.2762220
Abstract: We report state-to-state and total reaction probabilities for J=0 and total reaction probabilities for J=2 and 4 for the title reaction, both for ground-state and initially rovibrationally excited reactants. The results for three different potential energy surfaces are compared and contrasted. The potential energy surfaces employed are the DMBE IV surface by Pastrana et al. [J. Phys. Chem. 94, 8073 (1990)], the surface by Troe and Ushakov (TU) [J. Chem. Phys. 115, 3621 (2001)], and the new XXZLG ab initio surface by Xu et al. [J. Chem. Phys. 122, 244305 (2005)]. Our results show that the total reaction probabilities from both the TU and XXZLG surfaces are much smaller in magnitude for collision energies above 1.2eV compared to the DMBE IV surface. The three surfaces also show different behavior with regards to the effect of initial state excitation. The reactivity is increased on the XXZLG and the TU surfaces and decreased on the DMBE IV surface. Vibrational and rotational product state distributions for the XXZLG and the DMBE IV surface show different behaviors for both types of distributions. Our results show that for energies above 1.25eV the dynamics on the DMBE IV surface are not statistical. However, there is also evidence that the dynamics on the XXZLG surface are not purely statistical for energies above the onset of the first excited product vibrational state v′=1. The magnitude of the total reaction probability is decreased for J& for the DMBE IV and the XXZLG surfaces for ground-state reactants. However, for initially rovibrationally excited reactants, the total reaction probability does not decrease as expected for both surfaces. As a result the total cross section averaged over all Boltzmann accessible rotational states may well be larger than the cross section reported in the literature for j=1.
Understanding the high activity of mildly reduced graphene oxide electrocatalysts in oxygen reduction to hydrogen peroxide
Publisher: Royal Society of Chemistry (RSC)
Date: 2019
DOI: 10.1039/C9MH00066F
Abstract: The direct electrochemical synthesis of hydrogen peroxide (H 2 O 2 ) would provide an attractive alternative to the traditional anthraquinone oxidation process for continuous on-site applications.
Molecular orbital calculations of two-electron states for P-donor solid-state spin qubits
Publisher: American Physical Society (APS)
Date: 20-03-2006
Electronic Structure Shift of Deeply Nanoscale Silicon by
Si
Publisher:
American Physical Society (APS)
Date:
21-11-2019
Publisher: American Physical Society (APS)
Date: 21-11-2019
Hexagonal boron nitride and graphene in-plane heterostructures: An experimentally feasible approach to charge-induced switchable CO2 capture
Publisher: Elsevier BV
Date: 10-2016
Cooperative defect-enriched SiO2 for oxygen activation and organic dehydrogenation
Publisher: Elsevier BV
Date: 08-2019
An Ultra-Long-Life Flexible Lithium–Sulfur Battery with Lithium Cloth Anode and Polysulfone-Functionalized Separator
Publisher: American Chemical Society (ACS)
Date: 28-12-2020
Synthesis and Characterization of Colloidal Core–Shell Semiconductor Nanowires
Publisher: Wiley
Date: 24-08-2010
Abstract: CdSe colloidal nanowires, generated from solution‐liquid‐solid approach, have been coated with CdS rods (or ribbons) by using cadmium hexadecyl xanthate (Cd‐HDX) as a single source precursor. The use of different solvents and ligands causes pronounced effects on the morphology of the nanowires. The coating process includes nucleation and growth of CdS nanorods onto the core CdSe nanowires, followed by ripening of the CdS nanorods to produce the desired core‐shell nanowire structure.
A molecular-level strategy to boost the mass transport of perovskite electrocatalyst for enhanced oxygen evolution
Publisher: AIP Publishing
Date: 03-2021
DOI: 10.1063/5.0033912
Abstract: Perovskite oxides are of particular interest for the oxygen evolution reaction (OER) due to their high intrinsic activity. However, low surface area and nonpores in bulk phase generally limit the mass transport and thereby result in unsatisfactory mass activity. Herein, we propose a “molecular-level strategy” with the simultaneous modulation of the ordered pores on the oxygen-deficient sites along with sulfur (S) substitution on oxygen sites at the molecular level to boost the mass transport behavior of perovskite electrocatalyst for enhanced mass activity. As a proof of concept, the elaborately designed brownmillerite oxide Sr2Co1.6Fe0.4O4.8S0.2 (S-BM-SCF) shows approximately fourfold mass activity enhancement in 1 M KOH compared with the pristine SrCo0.8Fe0.2O3-δ (SCF) perovskite. Comprehensive experimental results, in combination with theoretical calculations, demonstrate that the intrinsic molecular-level pores in the brownmillerite structure can facilitate reactive hydroxyl ion (OH−) uptake into the oxygen-vacant sites and that S doping further promotes OH− adsorption by electronic structure modulation, thus accelerating mass transport rate. Meanwhile, the S-BM-SCF can significantly weaken the resistance of O2 desorption on the catalyst surface, facilitating the O2 evolution. This work deepens the understanding of how mass transport impacts the kinetics of the OER process and opens up a new avenue to design high-performance catalysts on the molecular level.
Model real-time quantum dynamical simulations of proton transfer in the green fluorescent protein (GFP)
Publisher: World Scientific Pub Co Pte Lt
Date: 12-2007
DOI: 10.1142/S0219633607003301
Abstract: In this paper, we present the results from model real-time quantum dynamical calculations of the proton transfer in green fluorescent protein (GFP) regarding four electronic states (labeled A, A*, I, I*). A coupled-states quantum wavepacket method has been used, which involves split-operator and fast FFT algorithms. The model potential energy surfaces are based upon data derived from experimental results with some modifications. Several important processes in GFP have been simulated, which include the photo-absorption and proton transfer in the excited state, the isotope effect and the recurrence time for proton motion in the excited state. The origin of the early-time (prompt) stimulated emission is tentatively explained in terms of off-resonance excitation as well as the contribution from the fastest component for proton transfer in GFP.
Defect Engineering in Graphene-Confined Single-Atom Iron Catalysts for Room-Temperature Methane Conversion
Publisher: American Chemical Society (ACS)
Date: 03-06-2021
The controlled disassembly of mesostructured perovskites as an avenue to fabricating high performance nanohybrid catalysts
Publisher: Springer Science and Business Media LLC
Date: 25-05-2017
DOI: 10.1038/NCOMMS15553
Abstract: Versatile superstructures composed of nanoparticles have recently been prepared using various disassembly methods. However, little information is known on how the structural disassembly influences the catalytic performance of the materials. Here we show how the disassembly of an ordered porous La 0.6 Sr 0.4 MnO 3 perovskite array, to give hexapod mesostructured nanoparticles, exposes a new crystal facet which is more active for catalytic methane combustion. On fragmenting three-dimensionally ordered macroporous (3DOM) structures in a controlled manner, via a process that has been likened to retrosynthesis, hexapod-shaped building blocks can be harvested which possess a mesostructured architecture. The hexapod-shaped perovskite catalyst exhibits excellent low temperature methane oxidation activity ( T 90% =438 °C reaction rate=4.84 × 10 −7 mol m −2 s −1 ). First principle calculations suggest the fractures, which occur at weak joints within the 3DOM architecture, afford a large area of (001) surface that displays a reduced energy barrier for hydrogen abstraction, thereby facilitating methane oxidation.
Time evolution in the unimolecular master equation at low temperatures: full spectral solution with scalable iterative methods and high precision
Publisher: Elsevier BV
Date: 11-2001
Autocatalytic Surface Reduction‐Assisted Synthesis of PtW Ultrathin Alloy Nanowires for Highly Efficient Hydrogen Evolution Reaction
Publisher: Wiley
Date: 27-01-2022
Abstract: Alloying noble metal catalysts with early transition metals (ETMs) has shown great promise by simultaneously boosting catalytic activity and durability because of their strong electronic interactions. However, the very negative reduction potential of ETMs has posed great challenges for the synthesis of the desired alloy catalysts, not to mention the structure‐controlled synthesis. Here an autocatalytic surface reduction‐assisted strategy is reported to realize the controllable synthesis of ultrathin PtW alloy nanowires (NWs). The experimental evidence and density functional theory (DFT) calculations demonstrate that the preformed Pt NWs in the synthesis serve as the catalyst to facilitate the reduction of W x + species through the autocatalytic surface reduction mechanism. Using the alkaline hydrogen evolution reaction (HER) as a model reaction, the as‐synthesized PtW NWs/C catalyst shows an ultralow overpotential of 18 mV at 10 mA cm –2 and a high mass activity of 6.13 A mg –1 Pt at an overpotential of 100 mV, ranking it among the most active catalysts. The dual roles of alloyed W atoms are further uncovered by theoretical simulations, involving the ensemble effect for accelerating H 2 O dissociation and a ligand effect for optimizing the hydrogen adsorption strength.
Full S matrix calculation via a single real-symmetric Lanczos recursion: The Lanczos artificial boundary inhomogeneity method
Publisher: AIP Publishing
Date: 13-01-2004
DOI: 10.1063/1.1640614
Abstract: We present an efficient and robust method for the calculation of all S matrix elements (elastic, inelastic, and reactive) over an arbitrary energy range from a single real-symmetric Lanczos recursion. Our new method transforms the fundamental equations associated with Light’s artificial boundary inhomogeneity approach [J. Chem. Phys. 102, 3262 (1995)] from the primary representation (original grid or basis representation of the Hamiltonian or its function) into a single tridiagonal Lanczos representation, thereby affording an iterative version of the original algorithm with greatly superior scaling properties. The method has important advantages over existing iterative quantum dynamical scattering methods: (a) the numerically intensive matrix propagation proceeds with real symmetric algebra, which is inherently more stable than its complex symmetric counterpart (b) no complex absorbing potential or real d ing operator is required, saving much of the exterior grid space which is commonly needed to support these operators and also removing the associated parameter dependence. Test calculations are presented for the collinear H+H2 reaction, revealing excellent performance characteristics.
HO2 Ro-vibrational bound-state calculations for large angular momentum: J=30, 40, and 50
Publisher: American Chemical Society (ACS)
Date: 03-02-2006
DOI: 10.1021/JP0582336
Abstract: The Lanczos homogeneous filter diagonalization method and the real Chebyshev filter diagonalization scheme incorporating doubling of the autocorrelation functions have been employed to compute the HO2 ro-vibrational states for high total angular momenta, J = 30, 40, and 50. For such computationally challenging calculations, we have adopted a parallel computing strategy to perform the matrix-vector multiplications. Low-lying bound states and high-lying bound states close to the dissociation threshold are reported. For low-lying bound states, a spectroscopic assignment has been attempted and the widely used approximate J-shifting method has been tested for this deep-well system. For high-lying bound states, the attempted spectroscopic assignments as well as the J-shifting approximation fail because of very strong Coriolis mixing, indicating that the Coriolis couplings are important for this system.
Unimolecular rovibrational bound and resonance states for large angular momentum: J=20 calculations for HO2
Publisher: AIP Publishing
Date: 07-2005
DOI: 10.1063/1.1949609
Abstract: We explore the calculation of unimolecular bound states and resonances for deep-well species at large angular momentum using a Chebychev filter diagonalization scheme incorporating doubling of the autocorrelation function as presented recently by Neumaier and Mandelshtam [Phys. Rev. Lett. 86, 5031 (2001)]. The method has been employed to compute the challenging J=20 bound and resonance states for the HO2 system. The methodology has firstly been tested for J=2 in comparison with previous calculations, and then extended to J=20 using a parallel computing strategy. The quantum J-specific unimolecular dissociation rates for HO2→H+O2 in the energy range from 2.114to2.596eV have been reported for the first time, and comparisons with the results of Troe and co-workers [J. Chem. Phys. 113, 11019 (2000) Phys. Chem. Chem. Phys. 2, 631 (2000)] from statistical adiabatic channel method/classical trajectory calculations have been made. For most of the energies, the reported statistical adiabatic channel method/classical trajectory rate constants agree well with the average of the fluctuating quantum-mechanical rates. Near the dissociation threshold, quantum rates fluctuate more severely, but their average is still in agreement with the statistical adiabatic channel method/classical trajectory results.
The 2.1Å Crystal Structure of the Far-red Fluorescent Protein HcRed: Inherent Conformational Flexibility of the Chromophore
Publisher: Elsevier BV
Date: 05-2005
DOI: 10.1016/J.JMB.2005.03.020
Abstract: We have determined the crystal structure of HcRed, a far-red fluorescent protein isolated from Heteractis crispa, to 2.1A resolution. HcRed was observed to form a dimer, in contrast to the monomeric form of green fluorescent protein (GFP) or the tetrameric forms of the GFP-like proteins (eqFP611, Rtms5 and DsRed). Unlike the well-defined chromophore conformation observed in GFP and the GFP-like proteins, the HcRed chromophore was observed to be considerably mobile. Within the HcRed structure, the cyclic tripeptide chromophore, Glu(64)-Tyr(65)-Gly(66), was observed to adopt both a cis coplanar and a trans non-coplanar conformation. As a result of these two conformations, the hydroxyphenyl moiety of the chromophore makes distinct interactions within the interior of the beta-can. These data together with a quantum chemical model of the chromophore, suggest the cis coplanar conformation to be consistent with the fluorescent properties of HcRed, and the trans non-coplanar conformation to be consistent with non-fluorescent properties of hcCP, the chromoprotein parent of HcRed. Moreover, within the GFP-like family, it appears that where conformational freedom is permissible then flexibility in the chromophore conformation is possible.
Study of the H+O2 reaction by means of quantum mechanical and statistical approaches: The dynamics on two different potential energy surfaces
Publisher: AIP Publishing
Date: 25-06-2008
DOI: 10.1063/1.2944246
Abstract: The possible existence of a complex-forming pathway for the H+O2 reaction has been investigated by means of both quantum mechanical and statistical techniques. Reaction probabilities, integral cross sections, and differential cross sections have been obtained with a statistical quantum method and the mean potential phase space theory. The statistical predictions are compared to exact results calculated by means of time dependent wave packet methods and a previously reported time independent exact quantum mechanical approach using the double many-body expansion (DMBE IV) potential energy surface (PES) [Pastrana et al., J. Phys. Chem. 94, 8073 (1990)] and the recently developed surface (denoted XXZLG) by Xu et al. [J. Chem. Phys. 122, 244305 (2005)]. The statistical approaches are found to reproduce only some of the exact total reaction probabilities for low total angular momenta obtained with the DMBE IV PES and some of the cross sections calculated at energy values close to the reaction threshold for the XXZLG surface. Serious discrepancies with the exact integral cross sections at higher energy put into question the possible statistical nature of the title reaction. However, at a collision energy of 1.6eV, statistical rotationally resolved cross sections managed to reproduce the experimental cross sections for the H+O2(v=0,j=1)→OH(v′=1,j′)+O process reasonably well.
High-precision timing of 42 millisecond pulsars with the European Pulsar Timing Array
Publisher: Oxford University Press (OUP)
Date: 02-03-2016
DOI: 10.1093/MNRAS/STW483
Nitrogen doping in ion-exchangeable layered tantalate towards visible-light induced water oxidation
Publisher: Royal Society of Chemistry (RSC)
Date: 2011
DOI: 10.1039/C0CC05440B
Lithium-metal polysulfide batteries with free-standing MoSxCy thin-film cathodes
Publisher: Elsevier BV
Date: 11-2021
CALCULATION OF HO 2 DENSITY OF STATES ON THREE POTENTIAL ENERGY SURFACES
Publisher: World Scientific Pub Co Pte Ltd
Date: 06-2010
DOI: 10.1142/S0219633610005918
Abstract: Density of states (DOS) in both bound and unimolecular dissociation regime for HO 2 system have been calculated quantum mechanically by Lanczos homogeneous filter diagonalization (LHFD) method. Three potential energy surfaces are explored and the results are contrasted for the total angular momentum J = 0 density of states. While two ab initio potential energy surfaces (PESs) (TU PES, J Chem Phys, 115:3621 and XXZLG PES, J Chem Phys122:244) produce the DOSs which are in fairly good agreement, the semi-empirical double many-body expansion (DMBE) IV PES (J Phys Chem94:8073) generates the much higher DOSs in higher energy range. The quantum mechanical DOSs are also compared with Troe et al.'s results from harmonic density, semiclassical density and their early density of states on the same TU ab initio surface.
Ultrasmall Water-Soluble and Biocompatible Magnetic Iron Oxide Nanoparticles as Positive and Negative Dual Contrast Agents
Publisher: Wiley
Date: 15-03-2012
Isolated copper–tin atomic interfaces tuning electrocatalytic CO2 conversion
Publisher: Springer Science and Business Media LLC
Date: 04-03-2021
DOI: 10.1038/S41467-021-21750-Y
Abstract: Direct experimental observations of the interface structure can provide vital insights into heterogeneous catalysis. Ex les of interface design based on single atom and surface science are, however, extremely rare. Here, we report Cu–Sn single-atom surface alloys, where isolated Sn sites with high surface densities (up to 8%) are anchored on the Cu host, for efficient electrocatalytic CO 2 reduction. The unique geometric and electronic structure of the Cu–Sn surface alloys (Cu 97 Sn 3 and Cu 99 Sn 1 ) enables distinct catalytic selectivity from pure Cu 100 and Cu 70 Sn 30 bulk alloy. The Cu 97 Sn 3 catalyst achieves a CO Faradaic efficiency of 98% at a tiny overpotential of 30 mV in an alkaline flow cell, where a high CO current density of 100 mA cm −2 is obtained at an overpotential of 340 mV. Density functional theory simulation reveals that it is not only the elemental composition that dictates the electrocatalytic reactivity of Cu–Sn alloys the local coordination environment of atomically dispersed, isolated Cu–Sn bonding plays the most critical role.
Numerical study of hydrogenic effective mass theory for an impurity P donor in Si in the presence of an electric field and interfaces
Publisher: American Physical Society (APS)
Date: 26-08-2003
Structural and Electronic Properties of Layered Arsenic and Antimony Arsenide
Publisher: American Chemical Society (ACS)
Date: 13-03-2015
Tailored Brownmillerite Oxide Catalyst with Multiple Electronic Functionalities Enables Ultrafast Water Oxidation
Publisher: American Chemical Society (ACS)
Date: 28-05-2021
Thermal Personalities of Older People in South Australia: A Personas-Based Approach to Develop Thermal Comfort Guidelines
Publisher: MDPI AG
Date: 13-11-2020
Abstract: An important consideration for future age-friendly cities is that older people are able to live in housing appropriate for their needs. While thermal comfort in the home is vital for the health and well-being of older people, there are currently few guidelines about how to achieve this. This study is part of a research project that aims to improve the thermal environment of housing for older Australians by investigating the thermal comfort of older people living independently in South Australia and developing thermal comfort guidelines for people ageing-in-place. This paper describes the approach fundamental for developing the guidelines, using data from the study participants’ and the concept of personas to develop a number of discrete “thermal personalities”. Hierarchical Cluster Analysis (HCA) was implemented to analyse the features of research participants, resulting in six distinct clusters. Quantitative and qualitative data from earlier stages of the project were then used to develop the thermal personalities of each cluster. The thermal personalities represent different approaches to achieving thermal comfort, taking into account a wide range of factors including personal characteristics, ideas, beliefs and knowledge, house type, and location. Basing the guidelines on thermal personalities highlights the heterogeneity of older people and the context-dependent nature of thermal comfort in the home and will make the guidelines more user-friendly and useful.
Reversibility relationship in collision-complex-forming bimolecular reactions
Publisher: American Chemical Society (ACS)
Date: 10-1997
DOI: 10.1021/JP970910B
A survey of mastitis pathogens including antimicrobial susceptibility in southeastern Australian dairy herds
Publisher: American Dairy Science Association
Date: 02-2022
Abstract: The objectives for this study were to (1) describe the pathogen profile in quarters from cows with clinical mastitis and in cows with subclinical mastitis in southeastern Australia and (2) describe antimicrobial susceptibility among isolated pathogens. As a secondary objective, we aimed to compare antimicrobial resistance prevalence in pathogens isolated from clinical and subclinical mastitis s les. A convenience s le of dairy herds (n = 65) from 4 regions in southeastern Australia (Gippsland, Northern Victoria, Tasmania, Western Victoria) were invited to submit milk s les from cows with clinical and subclinical mastitis over a 14-mo period (January 2011 to March 2012). Farmers were instructed to collect aseptic quarter milk s les from the first 10 cases of clinical mastitis for each month of the study. In addition, farmers submitted composite milk s les from cows with subclinical mastitis at 1 or 2 s ling occasions during the study period. Aerobic culture and biochemical tests were used to identify isolates. Isolates were classified as susceptible, intermediate, or resistant to a panel of antimicrobial agents based on the zone of growth inhibition around antimicrobial-impregnated disks, with antimicrobial resistance (AMR) classified as nonsusceptibility by combining intermediate and resistant groups into a single category. Generalized linear mixed models were used to compare the prevalence of AMR between clinical and subclinical mastitis isolates. For clinical mastitis s les (n = 3,044), 472 s les (15.5%) were excluded for contamination. Of the remaining s les (n = 2,572), the most common results were Streptococcus uberis (39.2%), no growth (27.5%), Staphylococcus aureus (10.6%), Escherichia coli (8.4%), and Streptococcus dysgalactiae (6.4%). For subclinical mastitis s les (n = 1,072), 425 (39.6%) were excluded due to contamination. Of the remaining s les (n = 647), the most common results were no growth (29.1%), Staph. aureus (29.1%), and Strep. uberis (21.6%). The prevalence of AMR among common isolates was low for the majority of antimicrobial agents. Exploratory analysis found that the probability of Staph. aureus demonstrating resistance to penicillin was 5.16 times higher (95% confidence interval: 1.68, 15.88) in subclinical isolates relative to clinical Staph. aureus isolates. A similar association was observed for amoxicillin with subclinical Staph. aureus isolates being 4.70 times (95% confidence interval: 1.49, 14.75) more likely to be resistant than clinical Staph. aureus isolates. We concluded that the most common bacteria causing clinical mastitis in dairy herds in Australia is likely to be Strep. uberis, whereas Staph. aureus is likely to be the most common cause of subclinical mastitis. Despite decades of antimicrobial use to control these organisms, AMR appears to be uncommon.
Orbital engineering of two-dimensional materials with hydrogenation: A realization of giant gap and strongly correlated topological insulators
Publisher: American Physical Society (APS)
Date: 23-07-2015
Intrinsic ORR Activity Enhancement of Pt Atomic Sites by Engineering the d‐Band Center via Local Coordination Tuning
Publisher: Wiley
Date: 26-08-2021
Abstract: A considerable amount of platinum (Pt) is required to ensure an adequate rate for the oxygen reduction reaction (ORR) in fuel cells and metal‐air batteries. Thus, the implementation of atomic Pt catalysts holds promise for minimizing the Pt content. In this contribution, atomic Pt sites with nitrogen (N) and phosphorus (P) co‐coordination on a carbon matrix (PtNPC) are conceptually predicted and experimentally developed to alter the d‐band center of Pt, thereby promoting the intrinsic ORR activity. PtNPC with a record‐low Pt content (≈0.026 wt %) consequently shows a benchmark‐comparable activity for ORR with an onset of 1.0 V RHE and half‐wave potential of 0.85 V RHE . It also features a high stability in 15 000‐cycle tests and a superior turnover frequency of 6.80 s −1 at 0.9 V RHE . Damjanovic kinetics analysis reveals a tuned ORR kinetics of PtNPC from a mixed 2/4‐electron to a predominately 4‐electron route. It is discovered that coordinated P species significantly shifts d‐band center of Pt atoms, accounting for the exceptional performance of PtNPC.
Hybrid Graphene and Graphitic Carbon Nitride Nanocomposite: Gap Opening, Electron–Hole Puddle, Interfacial Charge Transfer, and Enhanced Visible Light Response
Publisher: American Chemical Society (ACS)
Date: 27-02-2012
DOI: 10.1021/JA211637P
Abstract: Opening up a band gap and finding a suitable substrate material are two big challenges for building graphene-based nanodevices. Using state-of-the-art hybrid density functional theory incorporating long-range dispersion corrections, we investigate the interface between optically active graphitic carbon nitride (g-C(3)N(4)) and electronically active graphene. We find an inhomogeneous planar substrate (g-C(3)N(4)) promotes electron-rich and hole-rich regions, i.e., forming a well-defined electron-hole puddle, on the supported graphene layer. The composite displays significant charge transfer from graphene to the g-C(3)N(4) substrate, which alters the electronic properties of both components. In particular, the strong electronic coupling at the graphene/g-C(3)N(4) interface opens a 70 meV gap in g-C(3)N(4)-supported graphene, a feature that can potentially allow overcoming the graphene's band gap hurdle in constructing field effect transistors. Additionally, the 2-D planar structure of g-C(3)N(4) is free of dangling bonds, providing an ideal substrate for graphene to sit on. Furthermore, when compared to a pure g-C(3)N(4) monolayer, the hybrid graphene/g-C(3)N(4) complex displays an enhanced optical absorption in the visible region, a promising feature for novel photovoltaic and photocatalytic applications.
Activating Inert MXenes for Hydrogen Evolution Reaction via Anchored Metal Centers
Publisher: Wiley
Date: 23-11-2022
Abstract: Hydrogen evolution under alkaline conditions is still a challenge, due to the lack of active and cheap cathode materials. The reaction is controlled by the kinetics of water molecules dissociation, along with a balance between OH* desorption and H* recombination steps. The focus in this study is to investigate pathways to tune the activity of—the usually inert—MXenes via anchored metal atoms, which can act as active centers to facilitate the dissociation of water and the subsequent release of H 2 molecules. The most promising candidates are Fe anchored on V 2 CO 2 , Mn on Ti 2 CO 2 and V 2 CO 2 and Ir on Nb 2 CO 2 . These materials display low and facile H 2 O dissociation, with barriers as low as 0.25 eV in some cases, and favorable OH* desorption steps.
Vacancy mediated desorption of hydrogen from a sodium alanate surface: An ab initio spin-polarized study
Publisher: AIP Publishing
Date: 02-04-2007
DOI: 10.1063/1.2721127
Abstract: Ab initio spin-polarized density functional theory calculations are performed to explore the effect of single Na vacancy on NaAlH4(001) surface on the initial dehydrogenation kinetics. The authors found that two Al–H bond lengths become elongated and weakened due to the presence of a Na vacancy on the NaAlH4(001) surface. Spontaneous recombination from the surface to form molecular hydrogen is observed in the spin-polarized ab initio molecular dynamics simulation. The authors’ results indicate that surface Na vacancies play a critical role in accelerating the dehydrogenation kinetics in sodium alanate. The understanding gained here will aid in the rational design and development of complex hydride materials for hydrogen storage.
Facet-dependent carrier dynamics of cuprous oxide regulating the photocatalytic hydrogen generation
Publisher: Royal Society of Chemistry (RSC)
Date: 2022
DOI: 10.1039/D1MA00934F
Abstract: The photoactivity of rhombic dodecahedral Cu 2 O with dominant {110} facets is superior to that of cubic Cu 2 O with {100} surfaces partly owing to the improved charge separation and carrier mobility.
N-doped CsTaWO6 as a new photocatalyst for hydrogen production from water splitting under solar irradiation
Publisher: Wiley
Date: 09-11-2011
Si O 2 <
Publisher: American Physical Society (APS)
Date: 14-11-2018
Preparation of new sulfur-doped and sulfur/nitrogen co-doped CsTaWO6 photocatalysts for hydrogen production from water under visible light
Publisher: Royal Society of Chemistry (RSC)
Date: 2011
DOI: 10.1039/C0JM02549F
High activity and durability of novel perovskite electrocatalysts for water oxidation
Publisher: Royal Society of Chemistry (RSC)
Date: 2015
DOI: 10.1039/C5MH00096C
Abstract: Scandium and niobium co-doped strontium cobaltite perovskites are reported as a family of highly active and durable electrocatalysts for the OER in alkaline solution.
Molecular Modeling of Hydrotalcite Structure Intercalated with Transition Metal Oxide Anions: CrO42– and VO43–
Publisher: American Chemical Society (ACS)
Date: 26-10-2011
DOI: 10.1021/JP2079499
Abstract: Molecular dynamics (MD) simulations are used to study the interlayer structure, hydrogen bonding, and energetics of hydration of Mg/Al (2:1 and 4:1) layered double hydroxide (LDH) or hydrotalcite (HT) intercalated with oxymetal anions, CrO(4)(2-), and VO(4)(3-). The ab initio forcefield COMPASS is employed for the simulations. The charge on the oxymetal anions is determined by quantum mechanical density functional theory. The structural behavior of the oxymetal anions in LDH directly relates to the energetic relationships, with electrostatic and H-bonding interactions between the anions, hydroxide sites of the metal hydroxide layers, and the interlayer water molecules. Distinct minima in the hydration energy indicate the presence of energetically well-defined structural states with specific water content. The experimentally identified variability in the retention of the CrO(4)(2-) and VO(4)(3-) is well reflected in the calculations and self-diffusion coefficients obtained from the simulations give insight into the mobility of the intercalated species.
Titania-water interactions: a review of theoretical studies
Publisher: Royal Society of Chemistry (RSC)
Date: 2010
DOI: 10.1039/C0JM01491E
The effect of Fe doping on adsorption of CO2/N-2 within carbon nanotubes: a density functional theory study with dispersion corrections
Publisher: IOP Publishing
Date: 26-08-2009
DOI: 10.1088/0957-4484/20/37/375701
Abstract: An ab initio density functional theory (DFT) study with correction for dispersive interactions was performed to study the adsorption of N(2) and CO(2) inside an (8, 8) single-walled carbon nanotube. We find that the approach of combining DFT and van der Waals correction is very effective for describing the long-range interaction between N(2)/CO(2) and the carbon nanotube (CNT). Surprisingly, exohedral doping of an Fe atom onto the CNT surface will only affect the adsorption energy of the quadrupolar CO(2) molecule inside the CNT (20-30%), and not that of molecular N(2). Our results suggest the feasibility of enhancement of CO(2)/N(2) separation in CNT-based membranes by using exohedral doping of metal atoms.
First-Principle Study of Atomic Hydrogen Interaction with a Fluorinated Corannulene Radical
Publisher: CSIRO Publishing
Date: 2010
DOI: 10.1071/CH09442
Abstract: In this work, we study fluorination effects on atomic hydrogen interactions with the fluorinated corannulene radical (C15H10F5), which was built as a model for a partially fluorinated nanotube (or fullerene). Complete active space self-consistent field and multi-reference configuration interaction methods are employed to calculate the potential energy surfaces for both ground and excited electronic states, and the R-matrix quantum dynamics method is used to investigate the atomic hydrogen transmission and reflection dynamics through the five-membered ring in the fluorinated corannulene radical, which includes resonance effects as well as non-adiabatic transitions between the ground and excited electronic states. We also investigate hydrogen adsorptions at two sites in the middle five-membered ring, namely, on top of a carbon atom and in the middle of a carbon–carbon bond. We found that on carbon-top site, the adsorption is almost barrierless, whereas in the middle bond site, there is a barrier to hydrogen adsorption.
VARIATIONAL TRANSITION-STATE THEORY - A SIMPLE-MODEL FOR DISSOCIATION AND RECOMBINATION REACTIONS OF SMALL SPECIES
Publisher: American Chemical Society (ACS)
Date: 10-1991
DOI: 10.1021/J100175A050
Classical flux integrals in transition state theory: Generalized reaction coordinates
Publisher: AIP Publishing
Date: 08-1999
DOI: 10.1063/1.479453
Abstract: Transition state theory (TST) approximates the reactive flux in an elementary chemical reaction by the instantaneous flux passing through a hypersurface (the “transition state”) which completely ides the reactant and product regions of phase space. The rigorous classical evaluation of this instantaneous flux is carried out as a trace in phase space: effectively a multidimensional integral. We present an analysis of the momentum-space component of this flux integral for the case of a generalized reaction coordinate. The classic analysis of the canonical flux by Marcus [J. Chem. Phys. 41, 2624 (1964)] is refined by reducing the determinant which appears in the transition state partition function to a very simple form, facilitating the ensuing integration over coordinate space. We then extend the analysis to provide analytic expressions for the momentum flux integrals in both the energy-resolved, and the energy+angular-momentum-resolved microcanonical ensembles. These latter expressions allow substantial gains in the efficiency of microcanonical variational implementations of Transition State Theory with generalized reaction coordinates.
Electronic phase transitions under hydrostatic pressure in LaMnO3 (111) bilayers sandwiched between LaAlO3
Publisher: American Physical Society (APS)
Date: 13-01-2016
Kinetic isotope effect for ground state proton transfer in the green fluorescent protein: a quantum-kinetic model
Publisher: Royal Society of Chemistry (RSC)
Date: 2009
DOI: 10.1039/B912507H
Abstract: The calculated quantum mechanical kinetic isotope effects (KIE) agree nearly quantitatively with experimental KIE at room temperature.
European Pulsar Timing Array limits on an isotropic stochastic gravitational-wave background
Publisher: Oxford University Press (OUP)
Date: 31-08-2015
Mechanistic aspects of proton chain transfer in the green fluorescent protein - Part II. A comparison of minimal quantum chemical models
Publisher: Royal Society of Chemistry (RSC)
Date: 2007
DOI: 10.1039/B612760F
Abstract: In this paper we report the results of extensive quantum chemical reaction pathway calculations for the electronic ground state of several different cluster models that mimic the proton chain transfer path within the green fluorescent protein (GFP). Our principal objective is to establish the robustness with respect to variations in the model of our recent mechanistic inferences for the ground state proton chain transfer [S. Wang and S. C. Smith, J. Phys. Chem. B, 2006, 110, 5084]. Additionally, comparison of our ground state results with the excited state proton transfer (ESPT) study by Vendrell et al. [O. Vendrell, R. Gelabert, M. Moreno and J. M. Lluch, J. Am. Chem. Soc., 2006, 128, 3564] leads to the conclusion that the mechanism of proton chain transfer may be expected to be analogous in ground and excited states, principally because in both cases the loss of the chromophore's phenolic proton contributes strongly to the reaction coordinate only late in the reaction path.
Weak competing interactions control assembly of strongly bonded TCNQ ionic acceptor molecules on silver surfaces
Publisher: American Physical Society (APS)
Date: 19-09-2014
Borophene as a Promising Material for Charge-Modulated Switchable CO2 Capture
Publisher: American Chemical Society (ACS)
Date: 06-2017
Abstract: Ideal carbon dioxide (CO
New Insights on the Mechanism of Cyclization in Chromophore Maturation of Wild-Type Green Fluorescence Protein: A Computational Study
Publisher: American Chemical Society (ACS)
Date: 08-06-2016
Abstract: Cyclization is the first step in the chromophore maturation process of the green fluorescent protein (GFP). In our previous paper [J. Phys. Chem. B 2012, 116, 1426-1436], the results of molecular dynamics simulation suggested the possibility that the amide nitrogen atom of Gly67 attacks the carbonyl carbon of Ser65 directly to complete the cyclization process (one-step mechanism). In this paper, density functional theory (DFT) and quantum mechanical/molecular mechanical (QM/MM) calculations were undertaken to study this step reaction in detail. Three cluster model systems (model A, model B, and model C) and large protein system were set up to investigate the cyclization process. Our results indicate that the one-step mechanism only exists in the two minimum models. However, in model C and the large protein system, the cyclization mechanism involves two steps: the first step is proton of Gly67 amide nitrogen transferring to carbonyl oxygen of Ser65, generating protonated amide, which is stabilized by a hydrogen bond interaction with a crystallographic water molecule, and the second step is Gly67 amide nitrogen attacking the carbonyl carbon of Ser65. Arg96 plays an important role in promoting the cyclization. The energy of cyclized product relative to reactant is about 10.0 kcal/mol endothermic, which is in line with the experimental results.
Light, Catalyst, Activation: Boosting Catalytic Oxygen Activation Using a Light Pretreatment Approach
Publisher: American Chemical Society (ACS)
Date: 24-04-2017
Efficient time-independent wave packet scattering calculations within a Lanczos subspace: H+O-2 (J=0) state-to-state reaction probabilities
Publisher: AIP Publishing
Date: 08-02-2002
DOI: 10.1063/1.1429951
Abstract: An efficient Lanczos subspace method has been devised for calculating state-to-state reaction probabilities. The method recasts the time-independent wave packet Lippmann–Schwinger equation [Kouri et al., Chem. Phys. Lett. 203, 166 (1993)] inside a tridiagonal (Lanczos) representation in which action of the causal Green’s operator is affected easily with a QR algorithm. The method is designed to yield all state-to-state reaction probabilities from a given reactant-channel wave packet using a single Lanczos subspace the spectral properties of the tridiagonal Hamiltonian allow calculations to be undertaken at arbitrary energies within the spectral range of the initial wave packet. The method is applied to a H+O2 system (J=0), and the results indicate the approach is accurate and stable.
Sc and Nb dopants in SrCoO3 modulate electronic and vacancy structures for improved water splitting and SOFC cathodes
Publisher: Elsevier BV
Date: 10-2017
Photocatalytic hydrogen production from water using N-doped Ba 5 Ta4 O15 under solar irradiation
Publisher: American Chemical Society (ACS)
Date: 18-07-2011
DOI: 10.1021/JP202783T
A pseudospectral algorithm for the computation of transitional-mode eigenfunctions in loose transition states. II. Optimized primary and grid representations
Publisher: AIP Publishing
Date: 15-01-1999
DOI: 10.1063/1.478012
Abstract: A highly optimized pseudospectral algorithm is presented for effecting the exact action of a transitional-mode Hamiltonian on a state vector within the context of iterative quantum dynamical calculations (propagation, diagonalization, etc.). The method is implemented for the benchmark case of singlet dissociation of ketene. Following our earlier work [Chem. Phys. Lett. 243, 359 (1995)] the action of the kinetic energy operator is performed in a basis consisting of a direct product of Wigner functions. We show how one can compute an optimized (k,Ω) resolved spectral basis by diagonalizing a reference Hamiltonian (adapted from the potential surface at the given center-of-mass separation) in a basis of Wigner functions. This optimized spectral basis then forms the working basis for all iterative computations. Two independent transformations from the working basis are implemented: the first to the Wigner representation which facilitates the action of the kinetic energy operator and the second to an angular discrete variable representation (DVR) which facilitates the action of the potential energy operator. The angular DVR is optimized in relation to the reference Hamiltonian by standard procedures. In addition, a scheme which exploits the full sparsity of the kinetic energy operator in the Wigner representation has been devised which avoids having to construct full-length vectors in the Wigner representation. As a demonstration of the power and efficiency of this algorithm, all transitional mode eigenstates lying between the potential minimum and 100 cm−1 above threshold have been computed for a center-of-mass separation of 3 Å in the ketene system. The performance attributes of the earlier primitive algorithm and the new optimized algorithm are compared.
How to achieve maximum charge carrier loading on heteroatom-substituted graphene nanoribbon edges: density functional theory study
Publisher: Royal Society of Chemistry (RSC)
Date: 2012
DOI: 10.1039/C2JM31445B
Hydrotalcite intercalated siRNA: Computational characterization of the interlayer environment
Publisher: MDPI AG
Date: 07-06-2012
MICROSCOPIC RATE COEFFICIENTS IN REACTIONS WITH FLEXIBLE TRANSITION-STATES - ANALYSIS OF THE TRANSITIONAL-MODE SUM OF STATES
Publisher: AIP Publishing
Date: 09-1991
DOI: 10.1063/1.460846
Abstract: Expressions are derived for the energy- and angular-momentum-resolved transitional-mode sum of states, WTM(E,J), for flexible transition states in unimolecular, recombination, or bimolecular collision–complex-forming reactions. The expressions are derived classically by evaluation of the phase-space volume integral. The phase-space integral is so arranged that the total available momentum-space volume, Φ(E,J,q), for a frozen configuration q is first evaluated. Accurate analytic expressions for Φ(E,J,q) are obtained for all relevant pairwise combinations of atom, linear, spherical-top, symmetric-top, and asymmetric-top fragments in flexible transition states. The analytic expressions for Φ(E,J,q) indicate clearly the conditions under which the common method of imposing angular momentum conservation, which assumes that J≊L (L being the orbital angular momentum), will fail. WTM(E,J) is then obtained by integration of Φ(E,J,q) over configuration space. Exact evaluation of the integral over configuration space involves at most a five-dimensional numerical integral. Accurate analytical expressions for WTM(E,J) are derived for model potentials which admit sufficient flexibility for the fitting of more-accurate potentials. These expressions enable the calculation of accurate microscopic rate coefficients k(E,J) by microcanonical variational Rice–Ramsperger–Kassel–Marcus (RRKM) theory at little more computational expense than a standard RRKM calculation.
Prediction of absolute rate coefficients and product branching ratios for the C(P-3) plus allene reaction system
Publisher: AIP Publishing
Date: 30-09-2002
DOI: 10.1063/1.1506307
Abstract: Complex chemical reactions in the gas phase can be decomposed into a network of elementary (e.g., unimolecular and bimolecular) steps which may involve multiple reactant channels, multiple intermediates, and multiple products. The modeling of such reactions involves describing the molecular species and their transformation by reaction at a detailed level. Here we focus on a detailed modeling of the C(3P)+allene (C3H4) reaction, for which molecular beam experiments and theoretical calculations have previously been performed. In our previous calculations, product branching ratios for a nonrotating isomerizing unimolecular system were predicted. We extend the previous calculations to predict absolute unimolecular rate coefficients and branching ratios using microcanonical variational transition state theory (μ-VTST) with full energy and angular momentum resolution. Our calculation of the initial capture rate is facilitated by systematic ab initio potential energy surface calculations that describe the interaction potential between carbon and allene as a function of the angle of attack. Furthermore, the chemical kinetic scheme is enhanced to explicitly treat the entrance channels in terms of a predicted overall input flux and also to allow for the possibility of redissociation via the entrance channels. Thus, the computation of total bimolecular reaction rates and partial capture rates is now possible.
Initial rotational quantum state excitation and isotopic effects for the O(1D) + HCl -> OH + Cl (OCl + H) reaction
Publisher: World Scientific Pub Co Pte Lt
Date: 2009
DOI: 10.1142/S0219633609005209
Abstract: We present reaction probabilities, branching ratios and vibrational product quantum state distributions for the reaction O ( 1 D)+ HCl → OH+Cl (OCl+H) , Boltzmann averaged over initial rotational quantum states at a temperature of 300 K and also for the deuterium isotopic variant. The quantum scattering dynamics are performed using the potential energy surfaces for all three contributing electronic states. Comparisons are presented with results computed using only the ground electronic state potential energy surface, with results computed using only the j = 0 initial rotational state and also with results obtained using an equal weighting for the lowest 10 rotational states. Inclusion of the higher initial rotational states significantly changes the form of the reaction probability as a function of collision energy, reducing the threshold for reaction on the 1A" and 2A' excited electronic states. We found that the combined inclusion of higher initial rotational states and all three contributing electronic states is crucial for obtaining a branching ratio that is within the range and trend given by experiment from our J = 0 calculations. Isotopic effects range from tunnelling effects for the hydrogen variant and enhancement of reactivity for the production of OD on the excited electronic states.
Kinetics and Product Branching Ratios for the Reaction HCO + NO2
Publisher: American Chemical Society (ACS)
Date: 05-1995
DOI: 10.1021/J100019A033
Charge-modulated permeability and selectivity in graphdiyne for hydrogen purification
Publisher: Informa UK Limited
Date: 02-10-2016
Limits on Anisotropy in the Nanohertz Stochastic Gravitational Wave Background
Publisher: American Physical Society (APS)
Date: 22-07-2015
Oxygen Evolution Reaction: Boosting Oxygen Evolution Reaction by Creating Both Metal Ion and Lattice‐Oxygen Active Sites in a Complex Oxide (Adv. Mater. 1/2020)
Publisher: Wiley
Date: 2020
Conductive Boron-Doped Graphene as an Ideal Material for Electrocatalytically Switchable and High-Capacity Hydrogen Storage
Publisher: American Chemical Society (ACS)
Date: 18-11-2016
Abstract: Electrocatalytic, switchable hydrogen storage promises both tunable kinetics and facile reversibility without the need for specific catalysts. The feasibility of this approach relies on having materials that are easy to synthesize, possessing good electrical conductivities. Graphitic carbon nitride (g-C
Full Iterative Solution of the Two-Dimensional Master Equation for Thermal Unimolecular Reactions
Publisher: American Chemical Society (ACS)
Date: 1996
DOI: 10.1021/JP953430Y
First-principle studies of electronic structure and C-doping effect in boron nitride nanoribbon
Publisher: Elsevier BV
Date: 10-2007
Intercalation of sulfonate into layered double hydroxide: Comparison of simulation with experiment
Publisher: American Chemical Society (ACS)
Date: 18-12-2009
DOI: 10.1021/JP807411X
On the microscopic mechanism of carbon gasification: A theoretical study
Publisher: Elsevier BV
Date: 2004
Classical Koro and Koro-Like Symptoms: Illustration from Canada
Publisher: SAGE Publications
Date: 07-2021
DOI: 10.1177/26318318211028845
Abstract: Koro syndrome has been colorfully described as a pathological distortion of one’s body image of the genital organ. In Koro, body image dysphoria is characterized by severe anxiety related to the delusional idea that one’s genitals will shrink and retract into one’s abdomen, eventually leading to death. This syndrome was first reported in South East Asia, where endemics have been described, but it has also sporadically occurred globally. We present a systematic literature review on Koro syndrome and report 7 cases from Canada. A search review with PubMed and Google Scholar resulted in 504 entries. Sixty-seven manuscripts were eventually selected following a thorough elimination process. The resultant literature underscored the cultural ersity that underlay the reported cases. Various aspects of Koro have been examined (eg, etiological, clinical, diagnostic, and cultural aspects). It has stimulated substantial scholarly debate, discussions, correspondences, and arguments from anthropological, psychiatric, psychological, and biological perspectives. In our series, it seems that Koro could have been misattributed here. The primary concern was not with penile retraction of the cases. To our knowledge, this is the first time that a series of cases is documented from North America where the syndrome is often ignored. We highlight the potential differences between the classical Koro syndrome and a collection of beliefs related to the perception or delusion of penile retraction in other codable psychiatric disorders, Koro-like syndrome. Understanding Koro syndrome beyond geographic boundaries is in line with our collected case reports of Koro from outside Asia.
Correction: Controlling molecular ordering in solution-state conjugated polymers
Publisher: Royal Society of Chemistry (RSC)
Date: 2015
DOI: 10.1039/C5NR90161H
Abstract: Correction for 'Controlling molecular ordering in solution-state conjugated polymers' by J. Zhu et al., Nanoscale, 2015, DOI: 10.1039/c5nr02037a.
Confinement of Ionic Liquids at Single-Ni-Sites Boost Electroreduction of CO2 in Aqueous Electrolytes
Publisher: American Chemical Society (ACS)
Date: 29-10-2020
Effect of Dimerization on Vibrational Spectra of Eumelanin Precursors
Publisher: Wiley
Date: 05-2008
DOI: 10.1111/J.1751-1097.2007.00273.X
Abstract: We have synthesized a compound ideally suited to the study of structure-function relationships in eumelanin synthesis. N-methyl-5-hydroxy-6-methoxy-indole (MHMI) has key functional groups strategically placed on the indole framework to hinder binding in the 2, 5, 6 and 7 positions. Thus, the dimer bound exclusively in the 4-4' positions was isolated and characterized. In order to study the difference in vibrational structure between the MHMI monomer and dimer, Raman spectra were acquired of both compounds, as well as indole, indole-2-carboxylic acid and 5,6-dihydroxyindole-2-carboxylic acid (DHICA). Peaks were assigned to particular vibrational modes using B3LYP density functional theory calculations, and experimental and theoretical spectra displayed good agreement. Addition of functional groups to either benzene or pyrrole rings in the indole framework impacted vibrational spectra attributed to vibrations in either ring, and in some cases, peaks appearing unchanged between two compounds corresponded to different contributing vibrations. Dimerization resulted in an expected increase in the number of vibrational modes, but not a significant increase in the number of apparent peaks, as several modes frequently contributed to an in idual observed peak. Comparison of spectral features of the monomer and dimer provides insight into eumelanin photochemistry, but final conclusions depend on the planarity of oligomeric structure in vivo.
MEASURING THE MASS OF SOLAR SYSTEM PLANETS USING PULSAR TIMING
Publisher: American Astronomical Society
Date: 23-08-2010
A formation mechanism of oxygen vacancies in a MnO2 monolayer: A DFT + U study
Publisher: Royal Society of Chemistry (RSC)
Date: 2011
DOI: 10.1039/C1CP20634F
Abstract: Recently we reported the oxygen vacancy induced structural variations of the monolayer of manganese dioxide (MnO(2)) under the electronic irradiation. In this report, we further studied the formation mechanism of oxygen vacancies in a MnO(2) monolayer under the framework of density functional theory plus Hubbard model. The effect of injected electrons on the formation of oxygen vacancies has been investigated. It is believed that oxygen is most likely leaving in the form of neutral atoms or molecules. The origination of the role of negative charges has been particularly discussed.
Boosting Oxygen Evolution Reaction by Creating Both Metal Ion and Lattice-Oxygen Active Sites in a Complex Oxide
Publisher: Wiley
Date: 12-11-2020
Abstract: Developing efficient and low‐cost electrocatalysts for the oxygen evolution reaction (OER) is of paramount importance to many chemical and energy transformation technologies. The ersity and flexibility of metal oxides offer numerous degrees of freedom for enhancing catalytic activity by tailoring their physicochemical properties, but the active site of current metal oxides for OER is still limited to either metal ions or lattice oxygen. Here, a new complex oxide with unique hexagonal structure consisting of one honeycomb‐like network, Ba 4 Sr 4 (Co 0.8 Fe 0.2 ) 4 O 15 (hex‐BSCF), is reported, demonstrating ultrahigh OER activity because both the tetrahedral Co ions and the octahedral oxygen ions on the surface are active, as confirmed by combined X‐ray absorption spectroscopy analysis and theoretical calculations. The bulk hex‐BSCF material synthesized by the facile and scalable sol–gel method achieves 10 mA cm −2 at a low overpotential of only 340 mV (and small Tafel slope of 47 mV dec −1 ) in 0.1 m KOH, surpassing most metal oxides ever reported for OER, while maintaining excellent durability. This study opens up a new avenue to dramatically enhancing catalytic activity of metal oxides for other applications through rational design of structures with multiple active sites.
Summary of session C1: pulsar timing arrays
Publisher: Springer Science and Business Media LLC
Date: 09-07-2014
Synthesis, optical properties and theoretical modelling of discrete emitting states in doped silicon nanocrystals for bioimaging
Publisher: Royal Society of Chemistry (RSC)
Date: 2018
DOI: 10.1039/C8NR05071F
Abstract: The creation of multiple emission pathways in quantum dots (QDs) is an exciting prospect with fundamental interest and optoelectronic potential.
Surface-Induced Orientation Control of CuPc Molecules for the Epitaxial Growth of Highly Ordered Organic Crystals on Graphene
Publisher: American Chemical Society (ACS)
Date: 20-02-2013
DOI: 10.1021/JA3125096
Abstract: The epitaxial growth and preferred molecular orientation of copper phthalocyanine (CuPc) molecules on graphene has been systematically investigated and compared with growth on Si substrates, demonstrating the role of surface-mediated interactions in determining molecular orientation. X-ray scattering and diffraction, scanning tunneling microscopy, scanning electron microscopy, and first-principles theoretical calculations were used to show that the nucleation, orientation, and packing of CuPc molecules on films of graphene are fundamentally different compared to those grown on Si substrates. Interfacial dipole interactions induced by charge transfer between CuPc molecules and graphene are shown to epitaxially align the CuPc molecules in a face-on orientation in a series of ordered superstructures. At high temperatures, CuPc molecules lie flat with respect to the graphene substrate to form strip-like CuPc crystals with micrometer sizes containing monocrystalline grains. Such large epitaxial crystals may potentially enable improvement in the device performance of organic thin films, wherein charge transport, exciton diffusion, and dissociation are currently limited by grain size effects and molecular orientation.
Nanoporous Graphitic-C3N4@Carbon Metal-Free Electrocatalysts for Highly Efficient Oxygen Reduction
Publisher: American Chemical Society (ACS)
Date: 29-11-2011
DOI: 10.1021/JA209206C
Abstract: Based on theoretical prediction, a g-C(3)N(4)@carbon metal-free oxygen reduction reaction (ORR) electrocatalyst was designed and synthesized by uniform incorporation of g-C(3)N(4) into a mesoporous carbon to enhance the electron transfer efficiency of g-C(3)N(4). The resulting g-C(3)N(4)@carbon composite exhibited competitive catalytic activity (11.3 mA cm(-2) kinetic-limiting current density at -0.6 V) and superior methanol tolerance compared to a commercial Pt/C catalyst. Furthermore, it demonstrated significantly higher catalytic efficiency (nearly 100% of four-electron ORR process selectivity) than a Pt/C catalyst. The proposed synthesis route is facile and low-cost, providing a feasible method for the development of highly efficient electrocatalysts.
Electroreduction of CO2 to CO on a Mesoporous Carbon Catalyst with Progressively Removed Nitrogen Moieties
Publisher: American Chemical Society (ACS)
Date: 30-08-2018
Efficient Promotion of Anatase TiO2 Photocatalysis via Bifunctional Surface-Terminating Ti−O−B−N Structures
Publisher: American Chemical Society (ACS)
Date: 17-06-2009
DOI: 10.1021/JP900511U
Solvothermal Synthesis and Photoreactivity of Anatase TiO2 Nanosheets with Dominant {001} Facets
Publisher: American Chemical Society (ACS)
Date: 27-02-2009
DOI: 10.1021/JA808790P
Abstract: Owing to wide-ranging industrial applications and fundamental importance, tailored synthesis of well-faceted single crystals of anatase TiO(2) with high percentage of reactive facets has attracted much research interest. In this work, high-quality anatase TiO(2) single-crystal nanosheets mainly dominated by {001} facets have been prepared by using a water-2-propanol solvothermal synthetic route. The synergistic functions of 2-propanol and HF on the growth of anatase TiO(2) single-crystal nanosheets were studied by first-principle theoretical calculations, revealing that the addition of 2-propanol can strengthen the stabilization effect associated with fluorine adsorption over (001) surface and thus stimulate its preferred growth. By measuring the (*)OH species with terephthalic acid scavenger, the as-prepared anatase TiO(2) single-crystal nanosheets having 64% {001} facets show superior photoreactivity (more than 5 times), compared to P25 as a benchmarking material.
First principle study of proton transfer in the green fluorescent protein (GFP): Ab initio PES in a cluster model
Publisher: Elsevier BV
Date: 06-2012
Converged quantum calculations of HO2 bound states and resonances for J=6 and 10
Publisher: AIP Publishing
Date: 06-05-2004
DOI: 10.1063/1.1711811
Abstract: Bound and resonance states of HO2 are calculated quantum mechanically using both the Lanczos homogeneous filter diagonalization method and the real Chebyshev filter diagonalization method for nonzero total angular momentum J=6 and 10, using a parallel computing strategy. For bound states, agreement between the two methods is quite satisfactory for resonances, while the energies are in good agreement, the widths are in general agreement. The quantum nonzero-J specific unimolecular dissociation rates for HO2 are also calculated.
On the calculation of absolute spectral densities
Publisher: AIP Publishing
Date: 08-09-1996
DOI: 10.1063/1.472278
Abstract: A new method of calculating the absolute spectral density of a Hamiltonian operator is derived and discussed. The spectral density is expressed as the solution of an integral equation in which the kernel is a renormalized one-sided energy correlation function of the full microcanonical density operator and a microcanonical density operator for a reference Hamiltonian. The integral operator associated with this equation transforms a known spectral density function for the reference Hamiltonian into the spectral density of the full Hamiltonian. The integral equation, by virtue of its formulation in energy space, is inherently one-dimensional and offers no storage difficulties, and the elements of its kernel may be computed by applying the Lanczos algorithm to randomly selected eigenfunctions of the reference Hamiltonian. This spectral density correlation method offers a number of advantages over variational methods. In particular, it has the potential for overcoming the hitherto largely insurmountable problem of tracing over a multidimensional Hilbert space in order to compute the spectral density of a nonseparable molecular Hamiltonian.
Improved visible light absorption of HTaWO6 induced by nitrogen doping: An experimental and theoretical study
Publisher: Elsevier BV
Date: 2011
THE RELATIONSHIP BETWEEN RECOMBINATION, CHEMICAL ACTIVATION AND UNIMOLECULAR DISSOCIATION RATE COEFFICIENTS
Publisher: AIP Publishing
Date: 15-04-1989
DOI: 10.1063/1.455783
Abstract: A new solution to the master equation relating the rate coefficients for unimolecular, recombination (association) and chemical activation reactions, incorporating weak collision effects, is presented. The solution establishes conditions for the validity of the commonly used procedure of relating the recombination rate coefficient, throughout the falloff regime, to the reverse single-channel unimolecular rate coefficient via the equilibrium constant. In addition, a relationship between the rate coefficient for stabilization in a chemical activation reaction and the reverse multichannel unimolecular dissociation rate coefficient is derived. This result, in conjunction with recently developed methods for fully incorporating angular momentum conservation into the solution of the master equation for unimolecular dissociation, enables both angular momentum and weak collision effects to be accurately incorporated into the solution of the master equation for chemical activation reactions in the falloff regime. Application of this method to a typical ion/molecule chemical activation reaction, that of CH+3 with NH3, illustrates the importance of weak collision and angular momentum effects in this system.
Structure and Dynamics of Multiple Cationic Vectors−siRNA Complexation by All-Atomic Molecular Dynamics Simulations
Publisher: American Chemical Society (ACS)
Date: 28-06-2010
DOI: 10.1021/JP911913C
Abstract: Understanding the molecular mechanism of gene condensation is a key component to rationalizing gene delivery phenomena, including functional properties such as the stability of the gene-vector complex and the intracellular release of the gene. In this work, we adopt an atomistic molecular dynamics simulation approach to study the complexation of short strand duplex RNA with four cationic carrier systems of varying charge and surface topology at different charge ratios. At lower charge ratios, polymers bind quite effectively to siRNA, while at high charge ratios, the complexes are saturated and there are free polymers that are unable to associate with RNA. We also observed reduced fluctuations in RNA structures when complexed with multiple polymers in solution as compared to both free siRNA in water and the single polymer complexes. These novel simulations provide a much better understanding of key mechanistic aspects of gene-polycation complexation and thereby advance progress toward rational design of nonviral gene delivery systems.
Multiple hydrogen-bonded complexes based on 2-ureido-4[1H]-pyrimidinone: A theoretical study
Publisher: American Chemical Society (ACS)
Date: 07-09-2011
DOI: 10.1021/JP2061305
Abstract: In the present work, the electronic structures and properties of a series of 2-ureido-4[1H]-pyrimidinone(UPy)-based monomers and dimers in various environments (vacuum, chloroform, and water) are studied by density functional theoretical methods. Most dimers prefer to form a DDAA-AADD (D, H-bond donor A, H-bond acceptor) array in both vacuum and solvents. Topological analysis proved that intramolecular and intermolecular hydrogen bonds coexist in the dimers. Frequency and NBO calculations show that all the hydrogen bonds exhibit an obvious red shift in their stretching vibrational frequencies. Larger substituents at position 6 of the pyrimidinone ring with stronger electron-donating ability favor the total binding energy and free energy of dimerization. Calculations on the solvent effect show that dimerization is discouraged by the stronger polarity of the solvent. Further computations show that Dimer-1 may be formed in chloroform, but water molecules may interact with the donor or acceptor sites and hence disrupt the hydrogen bonds of Dimer-1.
A Structural Basis for the pH-dependent Increase in Fluorescence Efficiency of Chromoproteins
Publisher: Elsevier BV
Date: 05-2007
DOI: 10.1016/J.JMB.2007.02.007
Abstract: Within the fluorescent protein and chromoprotein family, the phenomenon of photoswitching is both intriguing and biotechnologically useful. Illumination of particular chromoproteins with intense light results in dramatic increases in fluorescence efficiency (termed kindling) and involves cis-trans isomerization of the chromophore. Here we report that chromophore isomerization can also be driven via alteration in pH. Specifically, we demonstrate that a number of naturally occurring chromoproteins, and their engineered variants, undergo a dramatic 20-100-fold increase in fluorescence efficiency at alkaline pH (>pH9.0). We have determined to 1.8 A resolution the structure of one such chromoprotein, Rtms5(H146S), in its highly far-red fluorescent form (Phi(F), 0.11 at pH 10.7) and compared it to the structure of the non-fluorescent form (Phi(F), 0.002 at pH 8.0). At high pH, the cyclic tri-peptide chromophore was observed to be mobile and distributed between a trans non-coplanar and a cis coplanar conformation, whereas at the lower pH, only a trans non-coplanar chromophore was observed. Calculation of pK(a) values suggested that titration of the side-chain of the conserved Glu215 close to the chromophore is involved in promoting the cis-coplanar conformation. Collectively, our data establish that isomerization to form a coplanar chromophore is a basis of the increased fluorescence efficiency at high pH. The phenomenon of pH-induced fluorescence gain has similarities with photoswitching, thereby providing a model to study the mechanism of kindling.
Structural and electronic properties of diazonium functionalized (4,4) single walled carbon nanotube: an ab initio study
Publisher: Informa UK Limited
Date: 20-12-2006
Quantum calculations for the S(1D) + H2 reaction employing the ground adiabatic electronic state
Publisher: IOP Publishing
Date: 06-07-2011
Half metallicty in finite-length zigzag single walled carbon nanotube: A first-principle prediction
Publisher: AIP Publishing
Date: 18-08-2008
DOI: 10.1063/1.2970055
Abstract: We predict here from first-principle calculations that finite-length (n,0) single walled carbon nanotubes (SWCNTs) with H-termination at the open ends displaying antiferromagnetic coupling when n is greater than 6. An opposite local gating effect of the spin states, i.e., half metallicity, is found under the influence of an external electric field along the direction of tube axis. Remarkably, boron doping of unpassivated SWCNTs at both zigzag edges is found to favor a ferromagnetic ground state, with the B-doped tubes displaying half-metallic behavior even in the absence of an electric field. Aside of the intrinsic interest of these results, an important avenue for development of CNT-based spintronic is suggested.
The simulation of outgoing-wave boundary conditions via a symmetrically damped, Hermitian Hamiltonian operator
Publisher: AIP Publishing
Date: 15-12-1997
DOI: 10.1063/1.475303
Abstract: A new method for simulating the effect of outgoing-wave boundary conditions in the calculation of quantum resonances is presented. The Hermitian Hamiltonian operator H is multiplied on each side by a d ing operator D, consisting of a real function d(R), which is unity in the resonance region and falls gradually to zero in the asymptotic region. The spectrum of the symmetrically d ed Hamiltonian operator, DHD is shown to provide an excellent approximation to the resonance energies of the Hamiltonian with outgoing-wave boundary conditions. Applications to the calculation of resonance energies for collinear H+H2 scattering and for HO2 dissociation are presented. In addition, we explore the feasibility of extracting resonance widths by using the DHD operator within a filter diagonalization (FD) scheme. Application of the FD scheme to HO2 yields encouraging results.
The effects of J-gate potential and interfaces on donor exchange coupling in the Kane quantum computer architecture
Publisher: IOP Publishing
Date: 06-02-2004
A COMPARATIVE STUDY OF ITERATIVE CHEBYSHEV AND LANCZOS IMPLEMENTATIONS OF THE BOUNDARY INHOMOGENEITY METHOD FOR QUANTUM SCATTERING
Publisher: World Scientific Pub Co Pte Lt
Date: 12-2003
DOI: 10.1142/S021963360300077X
Abstract: We have recently developed a scaleable Artificial Boundary Inhomogeneity (ABI) method [Chem. Phys. Lett.366, 390–397 (2002)] based on the utilization of the Lanczos algorithm, and in this work explore an alternative iterative implementation based on the Chebyshev algorithm. Detailed comparisons between the two iterative methods have been made in terms of efficiency as well as convergence behavior. The Lanczos subspace ABI method was also further improved by the use of a simpler three-term backward recursion algorithm to solve the subspace linear system. The two different iterative methods are tested on the model collinear H+H 2 reactive state-to-state scattering.
Numerical solution methods for large, difficult kinetic master equations
Publisher: Springer Science and Business Media LLC
Date: 19-08-2009
Theoretical study of two states reactivity of methane activation on iron atom and iron dimer
Publisher: Elsevier BV
Date: 06-2012
First-Principle Framework for Total Charging Energies in Electrocatalytic Materials and Charge-Responsive Molecular Binding at Gas-Surface Interfaces
Publisher: American Chemical Society (ACS)
Date: 20-04-2016
Abstract: Heterogeneous charge-responsive molecular binding to electrocatalytic materials has been predicted in several recent works. This phenomenon offers the possibility of using voltage to manipulate the strength of the binding interaction with the target gas molecule and thereby circumvent thermochemistry constraints, which inhibit achieving both efficient binding and facile release of important targets such as CO2 and H2. Stability analysis of such charge-induced molecular adsorption has been beyond the reach of existing first-principle approaches. Here, we draw on concepts from semiconductor physics and density functional theory to develop a first principle theoretical approach that allows calculation of the change in total energy of the supercell due to charging. Coupled with the calculated adsorption energy of gas molecules at any given charge, this allows a complete description of the energetics of the charge-induced molecular adsorption process. Using CO2 molecular adsorption onto negatively charged h-BN (wide-gap semiconductor) and g-C4N3 (half metal) as ex le cases, our analysis reveals that - while adsorption is exothermic after charge is introduced - the overall adsorption processes are not intrinsically spontaneous due to the energetic cost of charging the materials. The energies needed to overcome the barriers of these processes are 2.10 and 0.43 eV for h-BN and g-C4N3, respectively. This first principle approach opens up new pathways for a more complete description of charge-induced and electrocatalytic processes.
A comparison of an experimental unimolecular lifetime distribution with Rice–Ramsperger–Kassel–Marcus theory
Publisher: AIP Publishing
Date: 15-04-1994
DOI: 10.1063/1.467135
Abstract: The ion–molecule association system (CH+3/CH3CN) has been reexamined by the ion cyclotron double resonance technique. An experimental distribution of lifetimes has been measured for the collision complex (CH3CNCH+3)* formed in the association reaction between CH+3 and CH3CN. The experimental mean lifetime of the association complex formed within the ICR cell was 140 μs. A theoretical examination of the distribution of complex lifetimes using an RRKM model was also undertaken. The matrix of lifetimes for the various values of the total energy of the system (E) and the total angular momentum of the system (J) was obtained. This information was used to visualize the canonical ensemble of collision complexes in the ICR experiment in terms of their lifetimes. Once the distribution of lifetimes predicted by the model was modified to conform to experimental constraints, it was found to give a good approximation of the lifetime distribution determined experimentally. As a result of the new measurements of the complex lifetimes, we report absolute values of the collisional stabilization efficiencies. We also report rate coefficients for unimolecular dissociation and radiative relaxation.
Quantum dynamical study of the O(D1)+HCl reaction employing three electronic state potential energy surfaces
Publisher: AIP Publishing
Date: 07-01-2008
DOI: 10.1063/1.2813414
Abstract: Quantum dynamical calculations are reported for the title reaction, for both product arrangement channels and using potential energy surfaces corresponding to the three electronic states, 1A′1, 2A′1, and 1A″1, which correlate with both reactants and products. The calculations have been performed for J=0 using the time-dependent real wavepacket approach by Gray and Balint-Kurti [J. Chem. Phys. 108, 950 (1998)]. Reaction probabilities for both product arrangement channels on all three potential energy surfaces are presented for total energies between 0.1 and 1.1eV. Product vibrational state distributions at two total energies, 0.522 and 0.722eV, are also presented for both channels and all three electronic states. Product rotational quantum state distributions are presented for both product arrangement channels and all three electronic states for the first six product vibrational states.
Charge-controlled switchable H2 storage on conductive borophene nanosheet
Publisher: Elsevier BV
Date: 07-2019
Radiationless Decay of Red Fluorescent Protein Chromophore Models via Twisted Intramolecular Charge-Transfer States
Publisher: American Chemical Society (ACS)
Date: 25-01-2007
DOI: 10.1021/JA066430S
Abstract: We use CASSCF and MRPT2 calculations to characterize the bridge photoisomerization pathways of a model red fluorescent protein (RFP) chromophore model. RFPs are homologues of the green fluorescent protein (GFP). The RFP chromophore differs from the GFP chromophore via the addition of an N-acylimine substitution to a common hydroxybenzylidene-imidazolinone (HBI) motif. We examine the substituent effects on the manifold of twisted intramolecular charge-transfer (TICT) states which mediates radiationless decay via bridge isomerization in fluorescent protein chromophore anions. We find that the substitution destabilizes states associated with isomerization about the imidazolinone-bridge bond and stabilizes states associated with phenoxy-bridge bond isomerization. We discuss the results in the context of chromophore conformation and quantum yield trends in the RFP subfamily, as well as recent studies on synthetic models where the acylimine has been replaced with an olefin.
Phosphine vapor-assisted construction of heterostructured Ni2P/NiTe2 catalysts for efficient hydrogen evolution
Publisher: Royal Society of Chemistry (RSC)
Date: 2020
DOI: 10.1039/D0EE00666A
Abstract: A PH 3 vapor-assisted phase and structure engineering strategy to convert non-active NiTe into super-active Ni 2 P/NiTe 2 catalysts for hydrogen evolution reaction.
Methyl acrylatepolymerizations in the presence of a copper/N3S3macrobicyclic cage in DMSO at 25 °C
Publisher: Royal Society of Chemistry (RSC)
Date: 2010
DOI: 10.1039/B9PY00315K
Antipoisoning Nickel–Carbon Electrocatalyst for Practical Electrochemical CO2 Reduction to CO
Publisher: American Chemical Society (ACS)
Date: 21-10-2019
Quantum mechanical study of atomic hydrogen interaction with a fluorinated boron-substituted coronene radical
Publisher: IOP Publishing
Date: 18-03-2009
DOI: 10.1088/0953-8984/21/14/144209
Abstract: In this work we study the transmission of atomic hydrogen across a fluorinated boron-substituted coronene radical (C(19)H(12)BF(6)) as a model for partially fluorinated and boron-doped nanotubes or fullerenes. Complete active space self-consistent field (CASSCF) and multi-reference configuration interaction (MRCI) methods are employed to calculate the potential energy surfaces for both ground and excited electronic states, and one-dimensional R-matrix propagation is utilized to investigate the transmission/reflection dynamics of atomic hydrogen, through the central six-member ring of the fluorinated boron-substituted coronene radical. The quantum scattering includes resonance effects as well as non-adiabatic transitions between the ground and excited electronic states. Within the sudden approximation, both centre and off-centre approach trajectories have been investigated. Implications for atomic hydrogen encapsulation by carbon nanotube and fullerene are discussed.
Unraveling the Factors Behind the Efficiency of Hydrogen Evolution in Endohedrally Doped C60 Structures via Ab Initio Calculations and Insights from Machine Learning Models
Publisher: Wiley
Date: 25-01-2019
Intrinsic ultrasmall nanoscale silicon turns n-/p-type with SiO2/Si3N4-coating
Publisher: Beilstein Institut
Date: 23-08-2018
DOI: 10.3762/BJNANO.9.210
Abstract: Impurity doping of ultrasmall nanoscale (usn) silicon (Si) currently used in ultralarge scale integration (ULSI) faces serious miniaturization challenges below the 14 nm technology node such as dopant out-diffusion and inactivation by clustering in Si-based field-effect transistors (FETs). Moreover, self-purification and massively increased ionization energy cause doping to fail for Si nano-crystals (NCs) showing quantum confinement. To introduce electron- (n-) or hole- (p-) type conductivity, usn-Si may not require doping, but an energy shift of electronic states with respect to the vacuum energy between different regions of usn-Si. We show in theory and experiment that usn-Si can experience a considerable energy offset of electronic states by embedding it in silicon dioxide (SiO 2 ) or silicon nitride (Si 3 N 4 ), whereby a few monolayers (MLs) of SiO 2 or Si 3 N 4 are enough to achieve these offsets. Our findings present an alternative to conventional impurity doping for ULSI, provide new opportunities for ultralow power electronics and open a whole new vista on the introduction of p- and n-type conductivity into usn-Si.
Unimolecular decomposition of a polyatomic ion in a variable-temperature selected-ion-flow-drift tube: experiment and theoretical interpretation
Publisher: Elsevier BV
Date: 02-1990
Mg-Based Nanocomposites with High Capacity and Fast Kinetics for Hydrogen Storage
Publisher: American Chemical Society (ACS)
Date: 26-05-2006
DOI: 10.1021/JP057526W
Abstract: Magnesium and its alloys have shown a great potential in effective hydrogen storage due to their advantages of high volumetric/gravimetric hydrogen storage capacity and low cost. However, the use of these materials in fuel cells for automotive applications at the present time is limited by high hydrogenation temperature and sluggish sorption kinetics. This paper presents the recent results of design and development of magnesium-based nanocomposites demonstrating the catalytic effects of carbon nanotubes and transition metals on hydrogen adsorption in these materials. The results are promising for the application of magnesium materials for hydrogen storage, with significantly reduced absorption temperatures and enhanced ab/desorption kinetics. High level Density Functional Theory calculations support the analysis of the hydrogenation mechanisms by revealing the detailed atomic and molecular interactions that underpin the catalytic roles of incorporated carbon and titanium, providing clear guidance for further design and development of such materials with better hydrogen storage properties.
Quantum Mechanical Calculation of Energy Dependence of OCl/OH Product Branching Ratio and Product Quantum State Distributions for the O(1D) + HCl Reaction on All Three Contributing E
Publisher: American Chemical Society (ACS)
Date: 08-2008
DOI: 10.1021/JP803673Y
Abstract: OCl/OH product branching ratios are calculated as a function of total energy for the O( (1) D) + HCl reaction using quantum wavepacket methods. The calculations take account of reaction on all the three electronic state potential energy surfaces which correlate with both reactants and products. Our results show that reaction on the excited electronic state surfaces has a large effect on the branching ratio at higher energies and that these surfaces must therefore be fully taken into account. The calculations use the potential energy surfaces of Nanbu and co-workers. Product vibrational and rotational quantum state distributions are also calculated as a function of energy for both product channels. Inclusion of the excited electronic state potential energy surfaces improves the agreement of the predicted product vibrational quantum state distributions with experiment for the OH product channel. For OCl agreement between theory and experiment is retained for the vibrational quantum state distributions when the excited electronic state potential energy surfaces are included in the analysis. For the rotational state distributions good agreement between theory and experiment is maintained for energies at which experimental results are available. At higher energies, above 0.7 eV of total energy, the OCl rotational state distributions predicted using all three electronic state potential energy surfaces shift to markedly smaller rotational quantum numbers.
OH-initiated oxidation of toluene. 2. Master equation simulation of toluene oxide isomerization
Publisher: American Chemical Society (ACS)
Date: 18-01-2007
DOI: 10.1021/JP067113A
Abstract: In this work we continue our investigation of the toluene-OH-O2 system. We describe master equation modeling of the isomerization of toluene oxide, focusing on the formation of the cresols. A 15 isomer model is used. Simulations of both thermally activated processes and photolysis processes are described. In accord with experiment, it is found that photolysis with a high-energy light source should be expected to give a high yield of the thermal distribution of cresol products (dominated by the para isomer). Photolysis with a low-energy light source, on the other hand, favors formation of the thermally disfavored ortho isomer. Though the 15 isomer system is potentially an excellent test bed for the development of scalable master equation solution methods, existing scalable solution methods were found to fail on this system.
High-mobility anisotropic transport in few-layer γ-B28films
Publisher: Royal Society of Chemistry (RSC)
Date: 2016
DOI: 10.1039/C6NR07271B
Abstract: Recent reports of successful synthesis of atomically thin boron films have raised great prospects of discovering novel electronic and transport properties in a new type of 2D materials. Here we show by first-principles calculations that monolayer and bilayer γ-B
Fermi Level Determination for Charged Systems via Recursive Density of States Integration
Publisher: American Chemical Society (ACS)
Date: 03-07-2018
DOI: 10.1021/ACS.JPCLETT.8B01631
Abstract: Determining the Fermi level position for a given material is important to understand many of its electronic and chemical properties. Ab initio methods are effective in computing Fermi levels when using charge-neutral supercells. However, in the case where charges are explicitly included, the compensating homogeneous background charge, which is necessary to maintain charge neutrality in periodic models, causes the vacuum potential to be ill-defined - which would otherwise have been a reliable reference potential. Here, we develop a method based on recursively integrating the density of states to determine shifts in the Fermi level upon charging. By introducing incremental charges, one can compute the density of states profile and determine the shift in the Fermi level that corresponds to adding or removing a given increment of charge δq, which allows the evaluation of the Fermi level for any arbitrary charge q. We test this method for a range of materials (graphene, h-BN, C
Mobile Polaronic States in α-MoO3 : An ab Initio Investigation of the Role of Oxygen Vacancies and Alkali Ions
Publisher: American Chemical Society (ACS)
Date: 21-04-2016
Abstract: Some oxides have the ability to trap excess electrons in the form of small polarons. Here, using first-principles techniques, we investigate the interaction of excess electrons with α-MoO3. Polarons are found to be about 0.6 eV more stable than delocalized electrons. They can propagate with a high degree of anisotropicity along different crystallographic directions with the lowest barrier found to be about 0.08 eV. In addition to the band gap photoexcited charge carriers that can populate such polaron states, we investigate the role of oxygen vacancies as an intrinsic source of electrons. We also investigate intercalated alkali ions that can form complexes with the created polarons in the lattice. The alkali-polaron complex (AxMoO6, A = alkali ion) binding energies are relatively low, making it easy for the complex to dissociate. This, coupled with the low polaron migration energies, can generate a non-negligible contribution to electronic conductivity even in the absence of illumination, which is experimentally verified. Combined, this light-induced intercalation of alkali ion in MoO3 and its subsequent deintercalation (complex dissociation) processes lead to a novel self-photocharghing phenomenon.
The dynamics of the H++ D2reaction: a comparison of quantum mechanical wavepacket, quasi-classical and statistical-quasi-classical results
Publisher: Royal Society of Chemistry (RSC)
Date: 2010
DOI: 10.1039/B919914D
Abstract: A detailed study of the proton exchange reaction H(+) + D(2)(v = 0, j = 0) --> HD + D(+) on its ground 1(1)A' potential energy surface has been carried out using 'exact' close-coupled quantum mechanical wavepacket (WP-EQM), quasi-classical trajectory (QCT), and statistical quasi-classical trajectory (SQCT) calculations for a range of collision energies starting from the reaction threshold to 1.3 eV. The WP-EQM calculations include all total angular momenta up to J(max) = 50, and therefore the various dynamical observables are converged up to 0.6 eV. It has been found that it is necessary to include all Coriolis couplings to obtain reliable converged results. Reaction probabilities obtained using the different methods are thoroughly compared as a function of the total energy for a series of J values. Comparisons are also made of total reaction cross sections as function of the collision energy, and rate constants. In addition, opacity functions, integral cross sections (ICS) and differential cross sections (DCS) are presented at 102 meV, 201.3 meV and 524.6 meV collision energy. The agreement between the three sets of results is only qualitative. The QCT calculations fail to describe the overall reactivity and most of the dynamical observables correctly. At low collision energies, the QCT method is plagued by the lack of conservation of zero point energy, whilst at higher collision energies and/or total angular momenta, the appearance of an effective repulsive potential associated with the centrifugal motion "over" the well causes a substantial decrease of the reactivity. In turn, the statistical models overestimate the reactivity over the whole range of collision energies as compared with the WP-EQM method. Specifically, at sufficiently high collision energies the reaction cannot be deemed to be statistical and important dynamical effects seem to be present. In general the WP-EQM results lie in between those obtained using the QCT and SQCT methods. One of the main, unexpected, conclusions of this work is that an accurate description of the reaction and of its various dynamical features requires a computationally expensive, accurate quantum mechanical treatment.
Layered Graphene-Hexagonal BN Nanocomposites: Experimentally Feasible Approach to Charge-Induced Switchable CO2Capture
Publisher: Wiley
Date: 12-06-2015
Abstract: Recently, inducing negative charge density on hexagonal boron nitride (h-BN) has been predicted as an effective strategy for controllable, selective, and reversible CO2 capture. However, h-BN is a wide-gap semiconductor and it is not clear how to effectively induce the requisite negative charge density. In this paper, we employ first-principle calculations to propose hybrid h-BN-graphene (hybrid BN/G) nanosheets as an experimentally feasible strategy to induce charge on h-BN for charge-controlled CO2 capture. The results indicate that the charge density is effectively transferred from the graphene layer with high electronic mobility into the h-BN layer on the surface, regardless of the thickness of BN layers, such that CO2 capture/release can be simply controlled by switching on/off the charge states of hybrid BN/G system. In addition, these negatively charged hybrid BN/G are highly selective for separating CO2 from mixtures with CH4 , N2 , and/or H2 .
Implanting Ni-O-VOx sites into Cu-doped Ni for low-overpotential alkaline hydrogen evolution
Publisher: Springer Science and Business Media LLC
Date: 06-2020
DOI: 10.1038/S41467-020-16554-5
Abstract: Nickel-based catalysts are most commonly used in industrial alkaline water electrolysis. However, it remains a great challenge to address the sluggish reaction kinetics and severe deactivation problems of hydrogen evolution reaction (HER). Here, we show a Cu-doped Ni catalyst implanted with Ni-O-VOx sites (Ni(Cu)VOx) for alkaline HER. The optimal Ni(Cu)VOx electrode exhibits a near-zero onset overpotential and low overpotential of 21 mV to deliver –10 mA cm −2 , which is comparable to benchmark Pt/C catalyst. Evidence for the formation of Ni-O-VOx sites in Ni(Cu)VOx is established by systematic X-ray absorption spectroscopy studies. The VOx can cause a substantial d ening of Ni lattice and create an enlarged electrochemically active surface area. First-principles calculations support that the Ni-O-VOx sites are superactive and can promote the charge redistribution from Ni to VOx, which greatly weakens the H-adsorption and H 2 release free energy over Ni. This endows the Ni(Cu)VOx electrode high HER activity and long-term durability.
OH-initiated oxidation of toluene. 1. Quantum chemistry investigation of the reaction path
Publisher: American Chemical Society (ACS)
Date: 18-01-2007
DOI: 10.1021/JP067112I
Abstract: In this paper we present the results of a detailed quantum chemistry investigation of the toluene-OH-O2 system, mostly at the B3LYP/6-311G(2df,2pd) level. We focus on OH addition followed by H abstraction to O2, a mechanism based on that proposed by Klotz et al. [Phys. Chem. Chem. Phys. 2000, 2, 227] to explain the experimentally observed photolysis products. A notable feature of the calculated minimum energy pathway is the formation of ketone intermediates during the isomerization from the toluene oxides to the cresols. The quantum chemistry results largely support the plausibility of the mechanism proposed by Klotz et al. The system provides a rich set of reactions with which to test statistical kinetic theories.
Bridge‐ and Double‐Bonded O and NH on Fully OH‐ and NH 2 ‐Terminated Silicon Nanocrystals: Ground and Excited State Properties
Publisher: Wiley
Date: 27-02-2019
Iodine doped anatase TiO2 photocatalyst with ultra-long visible light response: correlation between geometric/electronic structures and mechanisms
Publisher: Royal Society of Chemistry (RSC)
Date: 2009
DOI: 10.1039/B820816F
Fabrication of Ultrasmall Si Encapsulated in Silicon Dioxide and Silicon Nitride as Alternative to Impurity Doping
Publisher: Wiley
Date: 08-06-2023
Abstract: Further miniaturization of complementary metal oxide semiconductor devices based on impurity‐doped semiconductors is limited due to statistical fluctuation of the impurity concentration in very small volumes and dopant deactivation, increasing the resistance and power consumption. Based on density functional theory calculations and backed by experimental data, the nanoscale electronic structure shift induced by anions at surfaces (NESSIAS) has been described recently. It explains the structure shift of low‐doped single‐crystalline Si nanowells (Si‐NWs) with thicknesses ≤3 nm embedded in SiO 2 (Si 3 N 4 ) toward n‐type (p‐type) behavior. The influence of the anions is on the scale of a few nanometers, allowing for very steep p–n junctions without the drawbacks of impurity doping. The process to fabricate crystalline silicon (c‐Si) NWs embedded in SiO 2 and Si 3 N 4 , starting with silicon on insulator (SOI) across 15 × 15 mm 2 s les, is described. Four possible methods to fabricate Si‐NWs by thinning down single‐crystalline top‐Si of an SOI substrate are evaluated in terms of reproducibility and surface roughness.
Formation and Migration of Oxygen Vacancies in SrCoO3 and Their Effect on Oxygen Evolution Reactions
Publisher: American Chemical Society (ACS)
Date: 27-07-2016
Reducible Disulfide-Based Non-Viral Gene Delivery Systems
Publisher: Bentham Science Publishers Ltd.
Date: 09-2009
DOI: 10.2174/138955709789055225
Abstract: The design and synthesis of safe efficient non-viral vectors for gene delivery has attracted significant attention in recent years due primarily to the severe side-effect profile reported with the use of their viral counterparts. Previous experiments have revealed that the strong interaction between the carriers and nucleic acid may well hinder the release of the gene from the complex in the cytosol adversely affecting transfection efficiency. However, incorporating reducible disulfide bonds within the delivery systems themselves which are then cleaved in the glutathione-rich intracellular environment may help in solving this puzzle. This review focuses on recent development of these reducible carriers. The biological rationale and approaches to the synthesis of reducible vectors are discussed in detail. The in vitro and in vivo evaluations of reducible carriers are also summarized and it is evident that they offer a promising approach in non-viral gene delivery system design.
Charge-modulated CO2 capture
Publisher: Elsevier BV
Date: 08-2017
Lanczos subspace time-independent wave packet calculations of S(D-1)+H-2 reactive scattering
Publisher: American Chemical Society (ACS)
Date: 06-2002
DOI: 10.1021/JP0139181
Temperature Dependence of Rate Coefficients and Branching Ratios for the NH 2 + NO Reaction via Microcanonical Variational Transition State Theory
Publisher: American Chemical Society (ACS)
Date: 1996
DOI: 10.1021/JP9602991
C-BN Single-Walled Nanotubes from Hybrid Connection of BN/C Nanoribbons: Prediction by ab initio Density Functional Calculations
Publisher: American Chemical Society (ACS)
Date: 16-01-2009
DOI: 10.1021/JA809053X
Abstract: We demonstrated for the first time by ab initio density functional calculation and molecular dynamics simulation that C(0.5)(BN)(0.5) armchair single-walled nanotubes (NT) are gapless semiconductors and can be spontaneously formed via the hybrid connection of graphene/BN Nanoribbons (GNR/BNNR) at room temperature. The direct synthesis of armchair C(0.5)(BN)(0.5) via the hybrid connection of GNR/BNNR is predicted to be both thermodynamically and dynamically stable. Such novel armchair C(0.5)(BN)(0.5) NTs possess enhanced conductance as that observed in GNRs. Additionally, the zigzag C(0.5)(BN)(0.5) SWNTs are narrow band gap semiconductors, which may have potential application for light emission. In light of recent experimental progress and the enhanced degree of control in the synthesis of GNRs and BNNR, our results highlight an interesting avenue for synthesizing a novel specific type of C(0.5)(BN)(0.5) nanotube (gapless or narrow direct gap semiconductor), with potentially important applications in BNC-based nanodevices.
Geographic Variation in Outpatient Antibiotic Prescribing Among Older Adults
Publisher: American Medical Association (AMA)
Date: 22-10-2012
DIFFREALWAVE: A parallel real wavepacket code for the quantum mechanical calculation of reactive state-to-state differential cross sections in atom plus diatom collisions
Publisher: Elsevier BV
Date: 10-2008
A density functional theory study on CO2 capture and activation by graphene-like boron nitride with boron vacancy
Publisher: Elsevier BV
Date: 10-2011
The pressure dependence of ion–molecule association rate coefficients
Publisher: AIP Publishing
Date: 02-1989
DOI: 10.1063/1.456055
Abstract: Two new techniques are presented for calculating the pressure dependence of ion/molecule association rates: (i) a semiclassical method of incorporating the effect of the hindered dipole rotation into an RRKM calculation of the microscopic rate coefficients k(E,J), and (ii) a solution for the master equation for unimolecular dissociation and recombination reactions, which incorporates angular momentum (J) conservation and is applicable when the moments of inertia of reactant and activated complex differ by a large amount. These techniques provide the optimal currently available means for calculating the pressure dependence of rate coefficients for ion–molecule reactions, which are highly sensitive to J-conservation effects. The method may be used for reliable estimates and fitting of experimental fall-off data. The new technique shows that Troe’s solution of the low-pressure J-conserving master equation is accurate for the nonequilibrium population distribution but overestimates (by up to a factor of 2) the rate coefficient extensions to Troe’s method to provide more accurate analytical approximations are derived. Application is presented to the association of CH3+ with HCN. The experimental pressure dependence, which cannot be fitted without proper accounting for J conservation, is fitted using the new treatment with values of ∼125 cm−1 for the average downward energy transfer for both rotational and internal energies. The new J-conservation method is also applicable to reactions of neutrals where the moment of inertia of the activated complex is more than six times that of the stable reactant.
Anatomy of the S(D-1)+H-2 reaction: the dynamics on two new potential energy surfaces from quantum dynamics calculations
Publisher: Royal Society of Chemistry (RSC)
Date: 2011
DOI: 10.1039/C1CP20127A
Abstract: We present exact quantum integral and differential cross sections for the title reaction from a time-dependent wavepacket method which takes account of all Coriolis couplings. We employ two new potential energy surfaces fitted using the double many-body expansion (DMBE) method. The difference between the two surfaces is that for the first the data was extrapolated to the complete basis set limit (CBS) and for the second the data was corrected semi-empirically (SEC). While the DMBE/CBS surface is, on first impressions, regarded as the most accurate, our results show that this surface gives consistent smaller cross section when compared to previous results employing an earlier surface, named Ho after its first author. We also find that the DMBE/CBS surface features an unphysical barrier for contracted H(2) distances which explains the smaller results. The DMBE/SEC surface, which is based on the same data, does not show the same barrier and the results compare much better to previous theoretical results as well as those from experiment. While we find that overall the differential cross sections from the DMBE/SEC surface are forward scattered, which is in line with experiment, the cross sections do not rise steeply enough with decreasing energy showing that this surface is not sufficiently attractive at low energies. We find this is due to a shallow van der Waals well present for the Ho surface but not on the DMBE surfaces.
Unique electronic structure induced high photoreactivity of sulfur-doped graphitic C3 N4
Publisher: American Chemical Society (ACS)
Date: 03-08-2010
DOI: 10.1021/JA103798K
Role of lithium vacancies in accelerating the dehydrogenation kinetics on a LiBH4 (010) surface: An ab initio study
Publisher: American Chemical Society (ACS)
Date: 21-07-2007
DOI: 10.1021/JP074096W
Charge-Dependent Dynamics of a Polyelectrolyte Dendrimer and Its Correlation with Invasive Water
Publisher: American Chemical Society (ACS)
Date: 19-03-2013
DOI: 10.1021/JA3125959
Abstract: Atomistic molecular dynamics (MD) simulations were carried out to investigate the local dynamics of polyelectrolyte dendrimers dissolved in deuterium oxide (D2O) and its dependence on molecular charge. Enhanced segmental dynamics upon increase in molecular charge is observed, consistent with quasielastic neutron scattering (QENS) measurements. A strong coupling between the intradendrimer local hydration level and segmental dynamics is also revealed. Compelling evidence shows these findings originate from the electrostatic interaction between the hydrocarbon components of a dendrimer and the invasive water. This combined study provides fundamental insight into the dynamics of charged polyelectrolytes and the solvating water molecules.
The mechanism of oxidation in chromophore maturation of wild-type green fluorescent protein: a theoretical study
Publisher: Royal Society of Chemistry (RSC)
Date: 2017
DOI: 10.1039/C6CP07983K
Abstract: DFT calculations suggested that the thermodynamically unfavourable cyclized product was trapped by oxidation.
Solving the unimolecular master equation with a weighted subspace projection method
Publisher: Wiley
Date: 06-2000
DOI: 10.1002/(SICI)1096-987X(200006)21:8<592::AID-JCC2>3.0.CO;2-2
Optimizing spectral indices and chemometric analysis of leaf chemical properties using radiative transfer modeling
Publisher: Elsevier BV
Date: 10-2011
Evidence for gravitational quadrupole moment variations in the companion of PSR J2051−0827
Publisher: Oxford University Press (OUP)
Date: 28-04-2011
Binding and Release between Polymeric Carrier and Protein Drug: pH-Mediated Interplay of Coulomb Forces, Hydrogen Bonding, van der Waals Interactions, and Entropy
Publisher: American Chemical Society (ACS)
Date: 02-10-2017
DOI: 10.1021/ACS.BIOMAC.7B00657
Abstract: The accelerating search for new types of drugs and delivery strategies poses challenge to understanding the mechanism of delivery. To this end, a detailed atomistic picture of binding between the drug and carrier is quintessential. Although many studies focus on the electrostatics of drug-vector interactions, it has also been pointed out that entropic factors relating to water and counterions can play an important role. By carrying out extensive molecular dynamics simulations and subsequently validating with experiments, we shed light herein on the binding in aqueous solution between a protein drug and polymeric carrier. We examined the complexation between the polymer poly(ethylene glycol) methyl ether acrylate-b-poly(carboxyethyl acrylate (PEGMEA-b-PCEA) and the protein egg white lysozyme, a system that acts as a model for polymer-vector rotein-drug delivery systems. The complexation has been visualized and characterized using contact maps and hydrogen bonding analyses for five independent simulations of the complex, each running over 100 ns. Binding at physiological pH is, as expected, mediated by Coulombic attraction between the positively charged protein and negatively charged carboxylate groups on the polymer. However, we find that consideration of electrostatics alone is insufficient to explain the complexation behavior at low pH. Intracomplex hydrogen bonds, van der Waals interactions, as well as water-water interactions dictate that the polymer does not release the protein at pH 4.8 or indeed at pH 3.2 even though the Coulombic attractions are largely removed as carboxylate groups on the polymer become titrated. Experiments in aqueous solution carried out at pH 7.0, 4.5, and 3.0 confirm the veracity of the computed binding behavior. Overall, these combined simulation and experimental results illustrate that coulomb interactions need to be complemented with consideration of other entropic forces, mediated by van der Waals interactions and hydrogen bonding, to search for adequate descriptors to predict binding and release properties of polymer-protein complexes. Advances in computational power over the past decade make atomistic molecular dynamics simulations such as implemented here one of the few avenues currently available to elucidate the complexity of these interactions and provide insights toward finding adequate descriptors. Thus, there remains much room for improvement of design principles for efficient capture and release delivery systems.
Ab initio studies of hydrogen desorption from low index magnesium hydride surface
Publisher: Elsevier BV
Date: 05-2006
Isolated Diatomic Ni‐Fe Metal–Nitrogen Sites for Synergistic Electroreduction of CO 2
Publisher: Wiley
Date: 17-04-2019
Abstract: Polynary single-atom structures can combine the advantages of homogeneous and heterogeneous catalysts while providing synergistic functions based on different molecules and their interfaces. However, the fabrication and identification of such an active-site prototype remain elusive. Here we report isolated diatomic Ni-Fe sites anchored on nitrogenated carbon as an efficient electrocatalyst for CO
Optimal spectral filtering in a finite subspace: a Lanczos-based implementation
Publisher: Royal Society of Chemistry (RSC)
Date: 1999
DOI: 10.1039/A808450E
Structured water in polyelectrolyte dendrimers: Understanding small angle neutron scattering results through atomistic simulation
Publisher: AIP Publishing
Date: 11-04-2012
DOI: 10.1063/1.3697479
Abstract: Based on atomistic molecular dynamics (MD) simulations, the small angle neutron scattering (SANS) intensity behavior of a single generation-4 polyelectrolyte polyamidoamine starburst dendrimer is investigated at different levels of molecular protonation. The SANS form factor, P(Q), and Debye autocorrelation function, γ(r), are calculated from the equilibrium MD trajectory based on a mathematical approach proposed in this work. The consistency found in comparison against previously published experimental findings (W.-R. Chen, L. Porcar, Y. Liu, P. D. Butler, and L. J. Magid, Macromolecules 40, 5887 (2007)) leads to a link between the neutron scattering experiment and MD computation, and fresh perspectives. The simulations enable scattering calculations of not only the hydrocarbons but also the contribution from the scattering length density fluctuations caused by structured, confined water within the dendrimer. Based on our computational results, we explore the validity of using radius of gyration RG for microstructure characterization of a polyelectrolyte dendrimer from the scattering perspective.
Erratum: Placing limits on the stochastic gravitational-wave background using European Pulsar Timing Array data
Publisher: Oxford University Press (OUP)
Date: 22-08-2012
Origin and Quantitative Description of the NESSIAS Effect at Si Nanostructures
Publisher: Wiley
Date: 18-03-2023
Abstract: The electronic structure of SiO 2 ‐ versus Si 3 N 4 ‐coated low nanoscale intrinsic silicon (Si) shifts away from versus toward the vacuum level E vac , originating from the Nanoscale Electronic Structure Shift Induced by Anions at Surfaces (NESSIAS). Using the quantum chemical properties of the elements involved to explain NESSIAS, an analytic parameter Λ is derived to predict the highest occupied energy level of Si nanocrystals (NCs) as verified by various hybrid‐density functional calculations and NC sizes. First experimental data of Si nanowells (NWells) embedded in SiO 2 versus Si 3 N 4 were measured by X‐ray absorption spectroscopy in total fluorescence yield mode (XAS‐TFY), complemented by ultraviolet photoelectron spectroscopy (UPS), characterizing their conduction band and valence band edge energies E C and E V , respectively. Scanning the valence band sub‐structure over NWell thickness yields an accurate estimate of E V shifted purely by spatial confinement, and thus the actual E V shift due to NESSIAS. Offsets of Δ E C = 0.56 eV and Δ E V = 0.89 eV were obtained for 1.9 nm thick NWells in SiO 2 versus Si 3 N 4 , demonstrating an intrinsic Si type II homojunction. This p/n junction generated by NESSIAS eliminates any deteriorating impact of impurity dopants, offering undoped ultrasmall Si electronic devices with much reduced physical gate lengths and CMOS‐compatible materials.
Unveiling the role of carbon oxidation in irreversible degradation of atomically-dispersed FeN4 moieties for proton exchange membrane fuel cells
Publisher: Royal Society of Chemistry (RSC)
Date: 2021
DOI: 10.1039/D0TA12105C
Abstract: Irreversible degradation of FeN 4 catalysts for proton exchange membrane fuel cells at the atomic level, caused by Fe de-metalation and chemical oxidation of carbon via a proposed new carbon oxidation pathway.
Higher charge/discharge rates of lithium-ions across engineered TiO2 surfaces leads to enhanced battery performance
Publisher: Royal Society of Chemistry (RSC)
Date: 2010
DOI: 10.1039/C0CC00832J
Abstract: Anatase TiO(2) having different percentages of (001)/(101) surface demonstrated different behaviors for Li(+) ions insertion and much enhanced rate performance of Li-ion batteries.
Dissociation dynamics of HeRh2+ in field-ion microscopy
Publisher: American Physical Society (APS)
Date: 04-2000
The Thermal Environment of Housing and Its Implications for the Health of Older People in South Australia: A Mixed-Methods Study
Publisher: MDPI AG
Date: 08-01-2022
Abstract: Older people are often over-represented in morbidity and mortality statistics associated with hot and cold weather, despite remaining mostly indoors. The study “Improving thermal environment of housing for older Australians” focused on assessing the relationships between the indoor environment, building characteristics, thermal comfort and perceived health/wellbeing of older South Australians over a study period that included the warmest summer on record. Our findings showed that indoor temperatures in some of the houses reached above 35 °C. With concerns about energy costs, occupants often use adaptive behaviours to achieve thermal comfort instead of using cooling (or heating), although feeling less satisfied with the thermal environment and perceiving health/wellbeing to worsen at above 28 °C (and below 15 °C). Symptoms experienced during hot weather included tiredness, shortness of breath, sleeplessness and dizziness, with coughs and colds, painful joints, shortness of breath and influenza experienced during cold weather. To express the influence of temperature and humidity on perceived health/wellbeing, a Temperature Humidity Health Index (THHI) was developed for this cohort. A health/wellbeing perception of “very good” is achieved between an 18.4 °C and 24.3 °C indoor operative temperature and a 55% relative humidity. The evidence from this research is used to inform guidelines about maintaining home environments to be conducive to the health/wellbeing of older people.
Chebyshev real wave packet propagation: H+O2 (J=0) state-to-state reactive scattering calculations
Publisher: AIP Publishing
Date: 27-08-2002
DOI: 10.1063/1.1499123
Abstract: In this paper we explore the relative performance of two recently developed wave packet methodologies for reactive scattering, namely the real wave packet Chebyshev domain propagation of Gray and Balint-Kurti [J. Chem. Phys. 108, 950 (1998)] and the Lanczos subspace wave packet approach of Smith et al. [J. Chem. Phys. 116, 2354 (2002) Chem. Phys. Lett. 336, 149 (2001)]. In the former method, a modified Schrödinger equation is employed to propagate the real part of the wave packet via the well-known Chebyshev iteration. While the time-dependent wave packet from the modified Schrödinger equation is different from that obtained using the standard Schrödinger equation, time-to-energy Fourier transformation yields wave functions which differ only trivially by normalization. In the Lanczos subspace approach the linear system of equations defining the action of the Green operator may be solved via either time-dependent or time-independent methods, both of which are extremely efficient due to the simple tridiagonal structure of the Hamiltonian in the Lanczos representation. The two different wave packet methods are applied to three dimensional reactive scattering of H+O2 (total J=0). State-to-state reaction probabilities, product state distributions, as well as initial-state-resolved cumulative reaction probabilities are examined.
N,P co-coordinated Fe species embedded in carbon hollow spheres for oxygen electrocatalysis
Publisher: Royal Society of Chemistry (RSC)
Date: 2019
DOI: 10.1039/C9TA03011E
Abstract: Carbon hollow spheres (FeNPC) with single-atomic and octahedral FeN x P y active sites are fabricated for oxygen electrocatalysis.
The International Pulsar Timing Array project: using pulsars as a gravitational wave detector
Publisher: IOP Publishing
Date: 06-04-2010
Molecular Modelling: All the Way from Atomistic Structure to Function in Complex Systems
Publisher: CSIRO Publishing
Date: 2010
DOI: 10.1071/CH10108
High-performance polymer photovoltaics based on rationally designed fullerene acceptors
Publisher: Elsevier BV
Date: 11-2013
Just add sugar for carbohydrate induced self-assembly of curcumin
Publisher: Springer Science and Business Media LLC
Date: 04-02-2019
DOI: 10.1038/S41467-019-08402-Y
Abstract: In nature, self-assembly processes based on hiphilic molecules play an integral part in the design of structures of higher order such as cells. Among them, hiphilic glycoproteins or glycolipids take on a pivotal role due to their bioactivity. Here we show that sugars, in particular, fructose, are capable of directing the self-assembly of highly insoluble curcumin resulting in the formation of well-defined capsules based on non-covalent forces. Simply by mixing an aqueous solution of fructose and curcumin in an open vessel leads to the generation of capsules with sizes ranging between 100 and 150 nm independent of the initial concentrations used. Our results demonstrate that hydrogen bonding displayed by fructose can induce the self-assembly of hydrophobic molecules such as curcumin into well-ordered structures, and serving as a simple and virtually instantaneous way of making nanoparticles from curcumin in water with the potential for template polymerization and nanocarriers.
The Role of Atomic Vacancy on Water Dissociation over Titanium Dioxide Nanosheet: A Density Functional Theory Study
Publisher: American Chemical Society (ACS)
Date: 17-01-2012
DOI: 10.1021/JP208951P
Measuring the mass of solar system planets using pulsar timing
Publisher: AIP
Date: 2011
DOI: 10.1063/1.3615087
Facile CO Oxidation on Oxygen‐functionalized MXenes via the Mars‐van Krevelen Mechanism
Publisher: Wiley
Date: 04-12-2020
Graphdiyne: a versatile nanomaterial for electronics and hydrogen purification
Publisher: Royal Society of Chemistry (RSC)
Date: 2011
DOI: 10.1039/C1CC15129K
Abstract: We theoretically extend the applications of graphdiyne, an experimentally available one-atom-thin carbon allotrope, to nanoelectronics and superior separation membrane for hydrogen purification on a precise level.
Nanosized anatase TiO2 single crystals for enhanced photocatalytic activity
Publisher: Royal Society of Chemistry (RSC)
Date: 2010
DOI: 10.1039/B919895D
Abstract: Nanosized anatase TiO(2) single crystals with 18% {001} facets have a raised conduction band minimum by 0.1 eV, and exhibit photocatalytic activity both for generating *OH radicals and for splitting water into hydrogen that is markedly superior--by factors of 5.6 and 8.2, respectively--to reference ca. 3 microm anatase TiO(2) with 72% {001} facets.
Boosting oxygen evolution reaction by activation of lattice‐oxygen sites in layered Ruddlesden‐Popper oxide
Publisher: Wiley
Date: 25-03-2020
DOI: 10.1002/EOM2.12021
The Elimination of Lanczos Ghosting Effects by MINRES Filter Diagonalization
Publisher: Elsevier BV
Date: 07-1998
Theory-guided construction of electron-deficient sites via removal of lattice oxygen for the boosted electrocatalytic synthesis of ammonia
Publisher: Springer Science and Business Media LLC
Date: 02-11-2020
Quantum Calculation of Ro-vibrational States: Methodology and DOCl Application Results
Publisher: American Chemical Society (ACS)
Date: 27-03-2008
DOI: 10.1021/JP8000114
Abstract: An improved Lanczos eigenvalue analysis method has been developed to compute the bound ro-vibrational states for the DOCl system at a total angular momentum of J = 0 and J = 30. In this method, the error norm is used to identify all the true eigenvalues, using the Lanczos algorithm without re-orthogonalization. For ro-vibrational spectroscopy calculations, the comparisons among experimental results, the exact quantum mechanical calculations, and the widely used approximate adiabatic rotation method have been made for J = 30. For J = 0, the density of states (DOS) in both the bound and unimolecular dissociation regime have been computed, whereas for the J = 30 case, only the DOS in the lower portion of the bound spectrum has been reported, because of substantial computational tasks.
Towards quantum mechanical characterization of the dissociation dynamics of ketene
Publisher: Royal Society of Chemistry (RSC)
Date: 1995
DOI: 10.1039/FD9950200017
Related Organisations
Related Funding Activities
Discovery Projects - Grant ID: DP0211019
Start Date: 2002
End Date: 12-2006
Amount: $330,000.00
Funder: Australian Research Council
View Funded ActivityDiscovery Projects - Grant ID: DP0771867
Start Date: 2007
End Date: 06-2010
Amount: $237,000.00
Funder: Australian Research Council
View Funded ActivityDiscovery Projects - Grant ID: DP1095906
Start Date: 2010
End Date: 07-2011
Amount: $365,000.00
Funder: Australian Research Council
View Funded ActivityDiscovery Projects - Grant ID: DP110101239
Start Date: 2011
End Date: 12-2017
Amount: $700,000.00
Funder: Australian Research Council
View Funded ActivitySpecial Research Initiatives - Grant ID: SR0354636
Start Date: 2004
End Date: 12-2004
Amount: $30,000.00
Funder: Australian Research Council
View Funded ActivityDiscovery Projects - Grant ID: DP170104853
Start Date: 2017
End Date: 12-2019
Amount: $312,500.00
Funder: Australian Research Council
View Funded ActivityLinkage Infrastructure, Equipment And Facilities - Grant ID: LE190100021
Start Date: 09-2019
End Date: 09-2022
Amount: $4,320,000.00
Funder: Australian Research Council
View Funded ActivityLinkage Infrastructure, Equipment And Facilities - Grant ID: LE160100051
Start Date: 2016
End Date: 12-2018
Amount: $3,000,000.00
Funder: Australian Research Council
View Funded ActivityLinkage Infrastructure, Equipment And Facilities - Grant ID: LE0882357
Start Date: 2008
End Date: 01-2009
Amount: $500,000.00
Funder: Australian Research Council
View Funded ActivityARC Centres Of Excellence - Grant ID: CE0348243
Start Date: 2003
End Date: 02-2015
Amount: $12,463,180.00
Funder: Australian Research Council
View Funded ActivitySpecial Research Initiatives - Grant ID: SR0354656
Start Date: 01-2004
End Date: 03-2005
Amount: $20,000.00
Funder: Australian Research Council
View Funded ActivitySpecial Research Initiatives - Grant ID: SR0354693
Start Date: 2004
End Date: 12-2004
Amount: $10,000.00
Funder: Australian Research Council
View Funded ActivityLinkage Infrastructure, Equipment And Facilities - Grant ID: LE110100126
Start Date: 05-2011
End Date: 12-2012
Amount: $150,000.00
Funder: Australian Research Council
View Funded Activity