ORCID Profile
0000-0003-3772-8057
Current Organisation
Griffith University
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Nanomaterials | Electrochemistry | Theoretical and Computational Chemistry not elsewhere classified | Physical Chemistry not elsewhere classified | Energy Generation, Conversion and Storage Engineering | Chemical Thermodynamics and Energetics | Theoretical and Computational Chemistry | Physical Chemistry (Incl. Structural)
Energy Storage (excl. Hydrogen) | Expanding Knowledge in the Chemical Sciences | Expanding Knowledge in the Physical Sciences |
Publisher: American Chemical Society (ACS)
Date: 09-02-2021
Publisher: American Chemical Society (ACS)
Date: 10-09-2019
Abstract: There is a growing demand for high-rate rechargeable batteries for powering electric vehicles and portable electronics. Here, we demonstrate a strategy for improving electrode performance by controlling the formation of solid electrolyte interphase (SEI). A composite electrode consisting of hard carbon (HC) and carbon nanotubes (CNTs) was used to study the formation of the SEI at different charging rates in an electrolyte consisting of 1 M NaClO
Publisher: American Chemical Society (ACS)
Date: 06-10-2021
Publisher: AIP Publishing
Date: 15-11-0017
DOI: 10.1063/1.5050421
Abstract: The surface tension of dilute salt water is a fundamental property that is crucial to understanding the complexity of many aqueous phase processes. Small ions are known to be repelled from the air-water surface leading to an increase in the surface tension in accordance with the Gibbs adsorption isotherm. The Jones-Ray effect refers to the observation that at extremely low salt concentration, the surface tension decreases. Determining the mechanism that is responsible for this Jones-Ray effect is important for theoretically predicting the distribution of ions near surfaces. Here we use both experimental surface tension measurements and numerical solution of the Poisson-Boltzmann equation to demonstrate that very low concentrations of surfactant in water create a Jones-Ray effect. We also demonstrate that the low concentrations of the surfactant necessary to create the Jones-Ray effect are too small to be detectable by surface sensitive spectroscopic measurements. The effect of surface curvature on this behavior is also examined, and the implications for unexplained bubble phenomena are discussed. This work suggests that the purity standards for water may be inadequate and that the interactions between ions with background impurities are important to incorporate into our understanding of the driving forces that give rise to the speciation of ions at interfaces.
Publisher: American Chemical Society (ACS)
Date: 11-07-2014
DOI: 10.1021/JP502887E
Abstract: Explaining and predicting the distribution of ions at the air-water interface has been a central challenge of physical chemistry for nearly a century. In essence, the problem amounts to calculating the change in the solvation energy of an ion as it approaches the interface. Here, we generalize our recently developed model of ionic solvation energies to calculate this interaction. The change in the Born energy as well as the static polarization response of the ion is included by using the conductor-like screening model (COSMO), which treats the ions quantum mechanically. Approximate expressions for the dispersion repulsion, cavity attraction, and surface potential contributions are also included. This model reproduces the surface tensions of electrolyte solutions and is consistent with ab initio molecular dynamics (MD) simulation. The model provides clear physical insight into iodide's adsorption. Unlike alternative models, no parameters are deliberately adjusted to reproduce surface tensions, and all of the important contributions to the interactions are included. Solving this problem has important direct implications for atmospheric chemistry and bubble properties. It also has important indirect implications for the more complex interactions of ions with protein and mineral surfaces. These play a fundamental role in a vast number of biological and industrial processes. The model is conceptually simple and has low computational demand, which facilitates its extension to these important applications.
Publisher: Royal Society of Chemistry (RSC)
Date: 2019
DOI: 10.1039/C9SE00099B
Abstract: The effective surface area utilization, carbon nanostructure and pores all contribute to high surface area-normalized capacitance.
Publisher: American Chemical Society (ACS)
Date: 24-03-2021
Publisher: Royal Society of Chemistry (RSC)
Date: 2020
DOI: 10.1039/D0CP04148C
Abstract: The solvation free energies of ions in water are consistent with the Born linear response model if the centre on which the ion–water repulsion force acts is moved from the oxygen atom towards the hydrogens.
Publisher: American Chemical Society (ACS)
Date: 29-01-2018
Abstract: Understanding the nature of ionic hydration at a fundamental level has eluded scientists despite intense interest for nearly a century. In particular, the microscopic origins of the asymmetry of ion solvation thermodynamics with respect to the sign of the ionic charge remains a mystery. Here, we determine the response of accurate quantum mechanical water models to strong nanoscale solvation forces arising from excluded volumes and ionic electrostatic fields. This is compared to the predictions of two important limiting classes of classical models of water with fixed point changes, differing in their treatment of "lone pair" electrons. Using the quantum water model as our standard of accuracy, we find that a single fixed classical treatment of lone pair electrons cannot accurately describe solvation of both apolar and cationic solutes, emphasizing the need for a more flexible description of local electronic effects in solvation processes. However, we explicitly show that all water models studied respond to weak long-ranged electrostatic perturbations in a manner that follows macroscopic dielectric continuum models, as would be expected. We emphasize the importance of these findings in the context of realistic ion models, using density functional theory and empirical models, and discuss the implications of our results for quantitatively accurate reduced descriptions of solvation in dielectric media.
Publisher: Elsevier BV
Date: 08-2015
Publisher: American Chemical Society (ACS)
Date: 08-09-2021
DOI: 10.26434/CHEMRXIV-2021-CX7QW-V2
Abstract: The osmotic/activity coefficients are one of the most fundamental and important properties of electrolyte solutions. There is currently no reliable means of predicting them from first principles without relying on extensive fitting to experimental measure- ments. The alkali hydroxide aqueous electrolytes are a particularly important class of solutions due to the crucial role they play in a vast range of applications. Here, for the first time we predict the osmotic/activity coefficients of these solutions without any fitting using a previously developed continuum solvent model of ion–ion interactions with no modifications. The feasibility of making these predictions with first princi- ples molecular simulation is also assessed. This demonstrates the reliability of this continuum solvent model and provides a plausible pathway to the fast and accurate prediction of these important properties for a wide range of electrolyte solutions.
Publisher: Elsevier BV
Date: 12-2011
Publisher: American Chemical Society (ACS)
Date: 11-06-2019
DOI: 10.26434/CHEMRXIV.10288314.V2
Abstract: Accurately predicting the molecular structure of solutions is a fundamental scientific challenge. Using quantum mechanical density functional theory (DFT) to make these predictions is hindered by significant variation depending on which DFT functional is used. Here, we present a simple metric that can determine the reliability of a DFT functional for predicting solvation structure. We then show that including a simple interaction term to correct this metric leads to quantitative agreement with experimental measurements of liquid structure. We demonstrate the utility of this method by using it to accurately describe the hydration structure around the Na+ and K+ ions as well as the structural properties of pure water with a computationally cheap functional.
Publisher: Cambridge University Press (CUP)
Date: 22-10-2021
DOI: 10.33774/CHEMRXIV-2021-7JXPQ-V2
Abstract: Accurately reproducing the structure of liquid water with ab initio molecular dynamics (AIMD) simulation is a crucial first step on the path towards accurately predicting the properties of liquid solutions without relying on experiment. Density functional theory (DFT) is normally used to approximate the forces in these simulations. However, no DFT functional has been shown to give an entirely satisfactory description of the structure of liquid water. Here, I propose a simple correction to the strongly constrained and appropriately normalised (SCAN) DFT functional, that corrects the strength of the hydrogen bonding interaction with a simple exponential potential fitted to dimer energy calculations. The resulting SCAN-CH functional provides an excellent description of the structure of liquid water. Long time scale NPT simulations are enabled by the use of neural network potentials, which demonstrate that the simulations are well converged and that the density of water is also more accurately reproduced with this method.
Publisher: American Chemical Society (ACS)
Date: 20-11-2019
DOI: 10.26434/CHEMRXIV.10288314.V1
Abstract: Accurately predicting the molecular structure of solutions is a fundamental scientific challenge. Using quantum mechanical density functional theory (DFT) to make these predictions is hindered by significant variation depending on which DFT functional is used. Here, we present a simple metric that can determine the reliability of a DFT functional for predicting solvation structure. We then show that including a simple interaction term to correct this metric leads to quantitative agreement with experimental measurements of liquid structure. We demonstrate the utility of this method by using it to accurately describe the hydration structure around the Na+ and K+ ions as well as the structural properties of pure water with a computationally cheap functional.
Publisher: American Chemical Society (ACS)
Date: 09-10-2018
DOI: 10.26434/CHEMRXIV.7149461.V2
Abstract: Supercapacitors cannot fulfill their potential as energy storage devices without substantially improving their comparatively low energy density. This requires improving their capacitance. Unfortunately, predicting the capacitance of the carbon-based materials that typically make up supercapacitor electrodes is difficult. For ex le, remarkably we lack a theoretical understanding of the capacitance of even the most basic ex le of a carbon electrode: highly oriented pyrolytic graphite. (HOPG) This material has a capacitance that is an order of magnitude lower than both standard metals and theoretical expectations. Here, we use new quantum mechanical calculations in combination with a critical analysis of the literature to demonstrate that the standard explanations of this unusually low capacitance are inadequate. We then demonstrate that a layer of hydrocarbon impurities which has recently been shown to form on graphite is the most plausible explanation. We develop a model of this effect which accounts for the penetration of solvent into the hydrocarbon layer as the voltage increases. This model explains the characteristic V shape of the capacitance as a function of voltage. Finally, we present evidence that this layer also forms and limits the capacitance in real supercapacitor materials such as activated carbon. Methods of modifying or removing this layer could therefore potentially lead to significant improvements in the capacitance of typical supercapacitors.
Publisher: American Chemical Society (ACS)
Date: 10-2018
DOI: 10.26434/CHEMRXIV.7149461.V1
Abstract: Supercapacitors cannot fulfill their potential as energy storage devices without substantially improving their comparatively low energy density. This requires improving their capacitance. Unfortunately, predicting the capacitance of the carbon-based materials that typically make up supercapacitor electrodes is difficult. For ex le, remarkably we lack a theoretical understanding of the capacitance of even the most basic ex le of a carbon electrode: highly oriented pyrolytic graphite. (HOPG) This material has a capacitance that is an order of magnitude lower than both standard metals and theoretical expectations. Here, we use new quantum mechanical calculations in combination with a critical analysis of the literature to demonstrate that the standard explanations of this unusually low capacitance are inadequate. We then demonstrate that a layer of hydrocarbon impurities which has recently been shown to form on graphite is the most plausible explanation. We develop a model of this effect which accounts for the penetration of solvent into the hydrocarbon layer as the voltage increases. This model explains the characteristic V shape of the capacitance as a function of voltage. Finally, we present evidence that this layer also forms and limits the capacitance in real supercapacitor materials such as activated carbon. Methods of modifying or removing this layer could therefore potentially lead to significant improvements in the capacitance of typical supercapacitors.
Publisher: AIP Publishing
Date: 23-03-2018
DOI: 10.1063/1.5020171
Abstract: The tetra-phenyl arsonium and tetra-phenyl borate (TATB) assumption is a commonly used extra-thermodynamic assumption that allows single ion free energies to be split into cationic and anionic contributions. The assumption is that the values for the TATB salt can be ided equally. This is justified by arguing that these large hydrophobic ions will cause a symmetric response in water. Experimental and classical simulation work has raised potential flaws with this assumption, indicating that hydrogen bonding with the phenyl ring may favor the solvation of the TB− anion. Here, we perform ab initio molecular dynamics simulations of these ions in bulk water demonstrating that there are significant structural differences. We quantify our findings by reproducing the experimentally observed vibrational shift for the TB− anion and confirm that this is associated with hydrogen bonding with the phenyl rings. Finally, we demonstrate that this results in a substantial energetic preference of the water to solvate the anion. Our results suggest that the validity of the TATB assumption, which is still widely used today, should be reconsidered experimentally in order to properly reference single ion solvation free energy, enthalpy, and entropy.
Publisher: The Royal Society
Date: 16-06-2017
Abstract: A theoretical model of haemoglobin is presented to explain an anomalous cationic Hofmeister effect observed in protein aggregation. The model quantifies competing proposed mechanisms of non-electrostatic physisorption and chemisorption. Non-electrostatic physisorption is stronger for larger, more polarizable ions with a Hofmeister series Li + K + Cs + . Chemisorption at carboxylate groups is stronger for smaller kosmotropic ions, with the reverse series Li + K + Cs + . We assess aggregation using second virial coefficients calculated from theoretical protein–protein interaction energies. Taking Cs + to not chemisorb, comparison with experiment yields mildly repulsive cation–carboxylate binding energies of 0.48 k B T for Li + and 3.0 k B T for K + . Aggregation behaviour is predominantly controlled by short-range protein interactions. Overall, adsorption of the K + ion in the middle of the Hofmeister series is stronger than ions at either extreme since it includes contributions from both physisorption and chemisorption. This results in stronger attractive forces and greater aggregation with K + , leading to the non-conventional Hofmeister series K + Cs + ≈ Li + .
Publisher: Elsevier BV
Date: 06-2016
Publisher: American Chemical Society (ACS)
Date: 02-2022
Abstract: Surfactant adsorption at the air-water interface is critical to many industrial processes but its dependence on salt ions is still poorly understood. Here, we investigate the adsorption of sodium dodecanoate onto the air-water interface using model saline waters of Li
Publisher: Elsevier BV
Date: 03-2023
Publisher: American Chemical Society (ACS)
Date: 12-10-2021
DOI: 10.26434/CHEMRXIV-2021-7JXPQ
Abstract: Accurately reproducing the structure of liquid water with ab initio molecular dynamics (AIMD) simulation is a crucial first step on the path towards accurately predicting the properties of liquid solutions without relying on experiment. Density functional theory (DFT) is normally used to approximate the forces in these simulations. However, no DFT functional has been shown to give an entirely satisfactory description of the structure of liquid water. Here, I propose a simple correction to the strongly constrained and appropriately normalised (SCAN) DFT functional, that corrects the strength of the hydrogen bonding interaction with a simple exponential potential fitted to dimer energy calculations. The resulting SCAN-CH functional provides an excellent description of the structure of liquid water. Long time scale NPT simulations are enabled by the use of neural network potentials, which demonstrate that the simulations are well converged and that the density of water is also more accurately reproduced with this method.
Publisher: American Chemical Society (ACS)
Date: 14-07-2020
DOI: 10.26434/CHEMRXIV.12645596.V1
Abstract: Accurate models of the free energies of ions in solution are crucial for understanding and modelling the huge number of important applications where electrolyte solutions play a crucial role such as electrochemical energy storage. The Born model, developed to describe ion solvation free energies, is widely considered to be critically flawed as it predicts a linear response of water to ionic charge, which fails to match water's supposed intrinsic preference to solvate anions over cations. Here, we demonstrate that this asymmetric response observed in simulation is the result of an arbitrary choice that the oxygen atom should be the centre of a water molecule. We show that an alternative and reasonable choice, which places the centre 0.5 Å towards the hydrogen atoms, results in a linear and charge symmetric response of water to ionic charge for a classical water model consistent with the Born model. This asymmetry should therefore be regarded as a property of the short range repulsive interaction not an intrinsic electrostatic property of water. We also show that this new water centre results in a more reasonable neutral cavity potential.
Publisher: Cambridge University Press (CUP)
Date: 12-10-2021
DOI: 10.33774/CHEMRXIV-2021-7JXPQ
Abstract: Accurately reproducing the structure of liquid water with ab initio molecular dynamics (AIMD) simulation is a crucial first step on the path towards accurately predicting the properties of liquid solutions without relying on experiment. Density functional theory (DFT) is normally used to approximate the forces in these simulations. However, no DFT functional has been shown to give an entirely satisfactory description of the structure of liquid water. Here, I propose a simple correction to the strongly constrained and appropriately normalised (SCAN) DFT functional, that corrects the strength of the hydrogen bonding interaction with a simple exponential potential fitted to dimer energy calculations. The resulting SCAN-CH functional provides an excellent description of the structure of liquid water. Long time scale NPT simulations are enabled by the use of neural network potentials, which demonstrate that the simulations are well converged and that the density of water is also more accurately reproduced with this method.
Publisher: American Chemical Society (ACS)
Date: 26-06-2020
Publisher: Royal Society of Chemistry (RSC)
Date: 2017
DOI: 10.1039/C7SC02138K
Abstract: Single ion solvation free energies are one of the most important properties of electrolyte solutions and yet there is ongoing debate about what these values are. Only the values for neutral ion pairs are known.
Publisher: American Chemical Society (ACS)
Date: 05-03-2014
DOI: 10.1021/JP410956M
Abstract: Continuum solvent models of electrolyte solutions are extremely useful. However, before we can use them with confidence, it is important to test them by comparison with a range of experimental properties. Here, we have adapted our recently developed1,2 simple continuum solvent model of ionic solvation free energies to calculate the solvation entropies and partial molar volumes of a group of monovalent and monatomic ions. This procedure gives good quantitative agreement for larger ions, and reproduces key qualitative features, such as the shift to positive entropies of solvation for iodide and the shift to negative partial molar volumes for small cations. Small ions require a correction to account for dielectric saturation effects, which brings them also into good agreement with experiment. We argue that this model does not require ad hoc corrections, and uses parameters that have good external physical justification. This work therefore establishes that our continuum solvent model can provide a satisfactory understanding of ionic solvation. It can thus serve as a foundation for improved models that explain and predict more complex ion specific effects.
Publisher: American Chemical Society (ACS)
Date: 21-10-2020
Publisher: American Chemical Society (ACS)
Date: 17-06-2021
Publisher: American Chemical Society (ACS)
Date: 06-02-2018
DOI: 10.26434/CHEMRXIV.5732976.V3
Abstract: The surface tension of dilute salt water is a fundamental property that is crucial to understanding the complexity of many aqueous phase processes. Small ions are known to be repelled from the air-water surface leading to an increase in the surface tension in accordance with the Gibbs adsorption isotherm. The Jones-Ray effect refers to the observation that at extremely low salt concentration the surface tension decreases in apparent contradiction with thermodynamics. Determining the mechanism that is responsible for this Jones-Ray effect is important for theoretically predicting the distribution of ions near surfaces. Here we show that this surface tension decrease can be explained by surfactant impurities in water that create a substantial negative electrostatic potential at the air-water interface. This potential strongly attracts positive cations in water to the interface lowering the surface tension and thus explaining the signature of the Jones-Ray effect. At higher salt concentrations, this electrostatic potential is screened by the added salt reducing the magnitude of this effect. The effect of surface curvature on this behavior is also examined and the implications for unexplained bubble phenomena is discussed. This work suggests that the purity standards for water may be inadequate and that the interactions between ions with background impurities are important to incorporate into our understanding of the driving forces that give rise to the speciation of ions at interfaces.
Publisher: American Chemical Society (ACS)
Date: 06-02-2018
DOI: 10.26434/CHEMRXIV.5732976.V2
Abstract: The surface tension of dilute salt water is a fundamental property that is crucial to understanding the complexity of many aqueous phase processes. Small ions are known to be repelled from the air-water surface leading to an increase in the surface tension in accordance with the Gibbs adsorption isotherm. The Jones-Ray effect refers to the observation that at extremely low salt concentration the surface tension decreases in apparent contradiction with thermodynamics. Determining the mechanism that is responsible for this Jones-Ray effect is important for theoretically predicting the distribution of ions near surfaces. Here we show that this surface tension decrease can be explained by surfactant impurities in water that create a substantial negative electrostatic potential at the air-water interface. This potential strongly attracts positive cations in water to the interface lowering the surface tension and thus explaining the signature of the Jones-Ray effect. At higher salt concentrations, this electrostatic potential is screened by the added salt reducing the magnitude of this effect. The effect of surface curvature on this behavior is also examined and the implications for unexplained bubble phenomena is discussed. This work suggests that the purity standards for water may be inadequate and that the interactions between ions with background impurities are important to incorporate into our understanding of the driving forces that give rise to the speciation of ions at interfaces.
Publisher: American Chemical Society (ACS)
Date: 27-12-2017
DOI: 10.26434/CHEMRXIV.5732976.V1
Abstract: The surface tension of dilute salt water is a fundamental property that is crucial to understanding the complexity of many aqueous phase processes. Small ions are known to be repelled from the air-water surface leading to an increase in the surface tension in accordance with the Gibbs adsorption isotherm. The Jones-Ray effect refers to the observation that at extremely low salt concentration the surface tension decreases in apparent contradiction with thermodynamics. Determining the mechanism that is responsible for this Jones-Ray effect is an important for theoretically predicting the distribution of ions near surfaces. Here we show that this surface tension decrease can be explained by surfactant impurities in water that create a substantial negative electrostatic potential at the air-water interface. This potential strongly attracts positive cations in water to the interface lowering the surface tension and thus explaining the signature of the Jones-Ray effect. At higher salt concentrations, this electrostatic potential is screened by the added salt reducing the magnitude of this effect. This work suggests that the purity standards for water may be inadequate and that the interactions between ions with background impurities are important to incorporate into our understanding of the driving forces that give rise to the speciation of ions at interfaces.
Publisher: American Chemical Society (ACS)
Date: 14-12-2018
DOI: 10.26434/CHEMRXIV.7466426.V1
Abstract: The ability to reproduce the structure of water around the sodium and potassium ions as determined by experiment is a key test of the quality of interaction potentials due to the central importance of these ions in a wide range of important phenomena. Here, we simulate the Na+ and K+ ions in bulk water using the recently developed strongly constrained and appropriately normed (SCAN) functional and compare with experimental X-ray diffraction (XRD) and X-ray adsorption fine structure (EXAFS) measurements to demonstrate that it accurately reproduces important structural details of the hydration structure of the sodium and potassium cations. We demonstrate that it performs substantially better than the generalized gradient approximation (GGA) based dispersion corrected revised Perdew, Burke, and Ernzerhof functional (revPBE-D3) and is even better than the random phase approximation level for potassium. Both of these functionals have been demonstrated to accurately reproduce the structure of bulk water. This improved performance compared with revPBE-D3 is attributed to smaller fluctuations of the mean error of ion-water cluster binding energies utilizing a novel benchmark for testing functionals.
Publisher: Royal Society of Chemistry (RSC)
Date: 2022
DOI: 10.1039/D2TA02610D
Abstract: Ab initio molecular dynamics can be massively accelerated using equivariant neural networks applicable to predict the properties of electrolyte solutions for predictive design in materials applications.
Publisher: Royal Society of Chemistry (RSC)
Date: 2019
DOI: 10.1039/C9TA05891E
Abstract: Microcrystalline cellulose-derived porous carbons with intrinsic defects and low-level nitrogen doping prepared at 600 °C exhibited both excellent electrocapacitive and electrocatalytic performances.
Publisher: American Chemical Society (ACS)
Date: 22-10-2021
DOI: 10.26434/CHEMRXIV-2021-7JXPQ-V2
Abstract: Accurately reproducing the structure of liquid water with ab initio molecular dynamics (AIMD) simulation is a crucial first step on the path towards accurately predicting the properties of liquid solutions without relying on experiment. Density functional theory (DFT) is normally used to approximate the forces in these simulations. However, no DFT functional has been shown to give an entirely satisfactory description of the structure of liquid water. Here, I propose a simple correction to the strongly constrained and appropriately normalised (SCAN) DFT functional, that corrects the strength of the hydrogen bonding interaction with a simple exponential potential fitted to dimer energy calculations. The resulting SCAN-CH functional provides an excellent description of the structure of liquid water. Long time scale NPT simulations are enabled by the use of neural network potentials, which demonstrate that the simulations are well converged and that the density of water is also more accurately reproduced with this method.
Publisher: Elsevier BV
Date: 10-2021
Publisher: American Chemical Society (ACS)
Date: 02-08-2022
DOI: 10.26434/CHEMRXIV-2022-5TLRZ
Abstract: Electrolyte solutions play a vital role in a vast range of important materials chemistry applications. For ex le, they are a crucial component in batteries, fuel cells, supercapacitors, electrolysis and carbon dioxide conversion/capture. Unfortunately, the determination of even their most basic properties from first principles remains an unsolved problem. As a result, the discovery and optimisation of electrolyte solutions for these applications largely relies on chemical intuition, experimental trial and error or empirical models. The challenge is that the dynamic nature of liquid electrolyte solutions require long simulation times to generate trajectories that sufficiently s le the configuration space the long range electrostatic interactions require large system sizes while the short range quantum mechanical (QM) interactions require an accurate level of theory. Fortunately, recent advances in the field of deep learning, specifically neural network potentials (NNPs), can enable significant accelerations in s ling the configuration space of electrolyte solutions. Here, we outline the implications of these recent advances for the field of materials chemistry and identify outstanding challenges and potential solutions.
Publisher: AIP Publishing
Date: 26-06-2017
DOI: 10.1063/1.4986284
Abstract: First principles molecular dynamics simulation protocol is established using revised functional of Perdew-Burke-Ernzerhof (revPBE) in conjunction with Grimme’s third generation of dispersion (D3) correction to describe the properties of water at ambient conditions. This study also demonstrates the consistency of the structure of water across both isobaric (NpT) and isothermal (NVT) ensembles. Going beyond the standard structural benchmarks for liquid water, we compute properties that are connected to both local structure and mass density fluctuations that are related to concepts of solvation and hydrophobicity. We directly compare our revPBE results to the Becke-Lee-Yang-Parr (BLYP) plus Grimme dispersion corrections (D2) and both the empirical fixed charged model (SPC/E) and many body interaction potential model (MB-pol) to further our understanding of how the computed properties herein depend on the form of the interaction potential.
Publisher: American Chemical Society (ACS)
Date: 16-10-2023
Publisher: American Chemical Society (ACS)
Date: 08-11-2019
DOI: 10.26434/CHEMRXIV.7466426.V2
Abstract: The ability to reproduce the experimental structure of water around the sodium and potassium ions is a key test of the quality of interaction potentials due to the central importance of these ions in a wide range of important phenomena. Here, we simulate the Na+ and K+ ions in bulk water using three density functional theory functionals: 1) The generalized gradient approximation (GGA) based dispersion corrected revised Perdew, Burke, and Ernzerhof functional (revPBE-D3) 2) The recently developed strongly constrained and appropriately normed (SCAN) functional 3) The random phase approximation (RPA) functional for potassium. We compare with experimental X-ray diffraction (XRD) and X-ray absorption fine structure (EXAFS) measurements to demonstrate that SCAN accurately reproduces key structural details of the hydra- tion structure around the sodium and potassium cations, whereas revPBE-D3 fails to do so. However, we show that SCAN provides a worse description of pure water in comparison with revPBE-D3. RPA also shows an improvement for K+, but slow convergence prevents rigorous comparison. Finally, we analyse cluster energetics to show SCAN and RPA have smaller fluctuations of the mean error of ion-water cluster binding energies compared with revPBE-D3.
Publisher: Royal Society of Chemistry (RSC)
Date: 2020
DOI: 10.1039/C9CP06161D
Abstract: The ability to reproduce the experimental structure of water around the sodium and potassium ions is a key test of the quality of interaction potentials due to the central importance of these ions in a wide range of important phenomena.
Publisher: American Chemical Society (ACS)
Date: 31-01-2023
DOI: 10.26434/CHEMRXIV-2023-45T1X
Abstract: We report the influence of ionomer and catalyst dispersion solvent interaction on the structure and ionomer film wettability in copper (Cu) catalyst layers (CLs) in a gas diffusion electrode (GDE). Our results show that acetone and methanol dispersion solvents interact differently with the perfluorinated sulfonic acid (PFSA) ionomer Aquivion, which is composed of hydrophobic backbones and hydrophilic ionic heads. Acetone solvates more with the hydrophobic backbones in the PFSA compared to methanol. Consequently, the ionomer film fabricated from casting Aquivion and acetone mixture on a flat surface is more continuous and hydrophobic than its methanol counterpart. Such ionomer-solvent interaction also leads to a more uniform and flooding-tolerant GDE when producing the copper catalyst layer with acetone (acetone-CL) compared to methanol (methanol-CL). As a result, acetone-CL yields higher selectivity to C2+ products at high current density, up to 29 % greater than methanol-CL at 500 mA cm-2. Ethylene is the primary product for both CLs, reaching 47.5 4.0 % and 43.9 5.5 % at 300 mA cm-2 for acetone-CL and methanol-CL, respectively. The improvement in C2+ product selectivity for the acetone-CL is attributed to the CLs high resistance against flooding at current densities above 300 mA cm-2. Our findings offer a new strategy to advance CO2 electrolysis by manipulating solvent-ionomer interactions.
Publisher: American Chemical Society (ACS)
Date: 20-02-2020
Publisher: American Chemical Society (ACS)
Date: 03-11-2021
Publisher: American Chemical Society (ACS)
Date: 08-2013
DOI: 10.1021/JP403596C
Abstract: Physically accurate continuum solvent models that can calculate solvation energies are crucial to explain and predict the behavior of solute particles in water. Here, we present such a model applied to small spherical ions and neutral atoms. It improves upon a basic Born electrostatic model by including a standard cavity energy and adding a dispersion component, consistent with the Born electrostatic energy and using the same cavity size parameter. We show that the well-known, puzzling differences between the solvation energies of ions of the same size is attributable to the neglected dispersion contribution. This depends on dynamic polarizability as well as size. Generally, a large cancellation exists between the cavity and dispersion contributions. This explains the surprising success of the Born model. The model accurately reproduces the solvation energies of the alkali halide ions, as well as the silver(I) and copper(I) ions with an error of 12 kJ mol(-1) (±3%). The solvation energy of the noble gases is also reproduced with an error of 2.6 kJ mol(-1) (±30%). No arbitrary fitting parameters are needed to achieve this. This model significantly improves our understanding of ionic solvation and forms a solid basis for the investigation of other ion-specific effects using a continuum solvent model.
Publisher: AIP Publishing
Date: 26-07-2017
DOI: 10.1063/1.4994912
Abstract: Determining the solvation free energies of single ions in water is one of the most fundamental problems in physical chemistry and yet many unresolved questions remain. In particular, the ability to decompose the solvation free energy into simple and intuitive contributions will have important implications for models of electrolyte solution. Here, we provide definitions of the various types of single ion solvation free energies based on different simulation protocols. We calculate solvation free energies of charged hard spheres using density functional theory interaction potentials with molecular dynamics simulation and isolate the effects of charge and cavitation, comparing to the Born (linear response) model. We show that using uncorrected Ewald summation leads to unphysical values for the single ion solvation free energy and that charging free energies for cations are approximately linear as a function of charge but that there is a small non-linearity for small anions. The charge hydration asymmetry for hard spheres, determined with quantum mechanics, is much larger than for the analogous real ions. This suggests that real ions, particularly anions, are significantly more complex than simple charged hard spheres, a commonly employed representation.
Publisher: Elsevier BV
Date: 07-2014
Publisher: American Chemical Society (ACS)
Date: 23-01-2019
Publisher: Springer Science and Business Media LLC
Date: 08-10-2018
DOI: 10.1038/S41557-018-0146-0
Abstract: The accurate dissection of binding energies into their microscopic components is challenging, especially in solution. Here we study the binding of noble gases (He-Xe) with the macrocyclic receptor cucurbit[5]uril in water by displacement of methane and ethane as
Publisher: Wiley
Date: 15-09-2022
Abstract: Dual‐carbon batteries (DCBs) with both electrodes composed of carbon materials are currently at the forefront of industrial consideration. This is due to their low cost, safety, sustainability, fast charging, and simpler electrochemistry than lithium and other post‐lithium metal‐ion batteries. This article provides an overview of the past lessons on rechargeable DCBs and their future promises. In brief, it introduces the reader to DCBs as one of the most promising energy storage solutions for balancing sustainability, cost and performance, their history, electrochemistry and associated charge storage mechanisms. Then, the past lessons with respect to their ion intercalation are provided. These include DCB mechanisms during different anion/cation intercalation in layered carbons and their intercalation compounds and electrode structures versus electrochemical performance. This is followed by a description of the current issues affecting DCBs like capacity fading and self‐discharging, electrolyte instability, low energy densities and electrode exfoliation, together with their remedies. Finally, an insightful perspective proposing key areas requiring significant research efforts toward the success of DCBs is provided responsible for accelerating the commercialization and adoption of DCBs toward a sustainable and circular economy. This article is a simplified guide to understanding the current state and future research needed to develop sustainable DCBs.
Publisher: Royal Society of Chemistry (RSC)
Date: 2021
DOI: 10.1039/D0CP06134D
Abstract: Expanded graphite with an interlayer distance of 4.4 Å enables sodium ion intercalation and thermodynamically most stable sodium-graphite intercalation compound can be formed when the interlayer distance reaches 6.0 Å.
Publisher: American Chemical Society (ACS)
Date: 08-2013
DOI: 10.1021/JP403595X
Abstract: The dispersion energy is an important contribution to the total solvation energies of ions and neutral molecules. Here, we present a new continuum model calculation of these energies, based on macroscopic quantum electrodynamics. The model uses the frequency dependent multipole polarizabilities of molecules in order to accurately calculate the dispersion interaction of a solute particle with surrounding water molecules. It includes the dipole, quadrupole, and octupole moment contributions. The water is modeled via a bulk dielectric susceptibility with a spherical cavity occupied by the solute. The model invokes d ing functions to account for solute-solvent wave function overlap. The assumptions made are very similar to those used in the Born model. This provides consistency and additivity of electrostatic and dispersion (quantum mechanical) interactions. The energy increases in magnitude with cation size, but decreases slightly with size for the highly polarizable anions. The higher order multipole moments are essential, making up more than 50% of the dispersion solvation energy of the fluoride ion. This method provides an accurate and simple way of calculating the notoriously problematic dispersion contribution to the solvation energy. The result establishes the importance of using accurate calculations of the dispersion energy for the modeling of solvation.
Publisher: American Chemical Society (ACS)
Date: 06-08-2020
DOI: 10.26434/CHEMRXIV.12768428.V1
Abstract: The osmotic/activity coefficients are one of the most fundamental and important properties of electrolyte solutions. There is currently no reliable means of predicting them from first principles without relying on extensive fitting to experimental measure- ments. The alkali hydroxide aqueous electrolytes are a particularly important class of solutions due to the crucial role they play in a vast range of applications. Here, for the first time we predict the osmotic/activity coefficients of these solutions without any fitting using a previously developed continuum solvent model of ion–ion interactions with no modifications. The feasibility of making these predictions with first princi- ples molecular simulation is also assessed. This demonstrates the reliability of this continuum solvent model and provides a plausible pathway to the fast and accurate prediction of these important properties for a wide range of electrolyte solutions.
Publisher: Elsevier BV
Date: 10-2022
Publisher: American Chemical Society (ACS)
Date: 09-06-2022
DOI: 10.26434/CHEMRXIV-2022-JNDLX
Abstract: Electrolyte solutions play a fundamental role in a vast range of important industrial and biological applications. Yet their thermodynamic and kinetic properties still can not be predicted from first principles. There are three central challenges that need to be overcome to achieve this. Firstly, the dynamic nature of these solutions requires long time scale simulations. Secondly, the long-range Coulomb interactions require large spatial scales. Thirdly, the short-range quantum mechanical (QM) interactions require an expensive level of QM theory. Here, we demonstrate a methodology to address these challenges. Data from a short \\emph{ab initio} molecular dynamics (AIMD) simulation of aqueous sodium chloride is used to train an equivariant graph neural network interatomic potential (NNP) that can reliably reproduce the short-range QM forces and energies at a moderate computational cost. This NNP is combined with a continuum solvent description of the long-range electrostatic interactions to enable stable long time and large spatial scale simulations. From these simulations, ion-water and ion-ion radial distribution functions (RDFs), as well as ionic diffusivities, can be determined. The ion-ion RDFs are then used in a continuum solvent approach to calculate the osmotic and activity coefficients. Good experimental agreement is demonstrated up to the solubility limit of sodium chloride in water. This result implies that classical electrostatic theory can describe electrolyte solution over a remarkably wide concentration range as long as it is combined with an accurate description of the short-range interactions. This approach should be applicable to determine the thermodynamic and kinetic properties of many important electrolyte solutions for which experimental data is insufficient.
Publisher: American Chemical Society (ACS)
Date: 07-09-2021
Publisher: Royal Society of Chemistry (RSC)
Date: 2014
DOI: 10.1039/C4CP02822H
Abstract: We present a continuum solvent model of ion–ion interactions in water that reproduces activities with only two fitted parameters.
Publisher: American Chemical Society (ACS)
Date: 26-05-2020
Publisher: Royal Society of Chemistry (RSC)
Date: 2023
DOI: 10.1039/D3CP00903C
Abstract: Binding of F-diglyme and OH-diglyme derivatives could be effectively used to tune the co-intercalation of Na into graphite.
Publisher: Cambridge University Press (CUP)
Date: 08-09-2021
DOI: 10.33774/CHEMRXIV-2021-CX7QW-V2
Abstract: The osmotic/activity coefficients are one of the most fundamental and important properties of electrolyte solutions. There is currently no reliable means of predicting them from first principles without relying on extensive fitting to experimental measure- ments. The alkali hydroxide aqueous electrolytes are a particularly important class of solutions due to the crucial role they play in a vast range of applications. Here, for the first time we predict the osmotic/activity coefficients of these solutions without any fitting using a previously developed continuum solvent model of ion–ion interactions with no modifications. The feasibility of making these predictions with first princi- ples molecular simulation is also assessed. This demonstrates the reliability of this continuum solvent model and provides a plausible pathway to the fast and accurate prediction of these important properties for a wide range of electrolyte solutions. / / /
Start Date: 06-2020
End Date: 07-2023
Amount: $400,000.00
Funder: Australian Research Council
View Funded ActivityStart Date: 06-2020
End Date: 03-2024
Amount: $419,000.00
Funder: Australian Research Council
View Funded Activity