ORCID Profile
0000-0002-6501-4513
Current Organisation
Universitat Politècnica de Catalunya
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.
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.
Materials engineering | Nanotechnology | Environmental Nanotechnology | Condensed Matter Modelling and Density Functional Theory | Functional materials | Composite and hybrid materials | Nanoelectronics
Expanding Knowledge in the Physical Sciences | Solar-Photovoltaic Energy | Expanding Knowledge in Technology |
Publisher: Elsevier BV
Date: 07-2011
Publisher: Wiley
Date: 27-12-2017
Publisher: American Chemical Society (ACS)
Date: 08-06-2018
Abstract: Magnetic materials with large magnetic anisotropy are essential for workaday applications such as permanent magnets and magnetic data storage. There is widespread interest in finding efficient ways of controlling magnetic anisotropy, among which strain control has proven to be a very powerful technique. Here, we demonstrate the strain-mediated magnetic anisotropy in SrCoO
Publisher: American Physical Society (APS)
Date: 16-02-2012
Publisher: American Chemical Society (ACS)
Date: 13-05-2011
DOI: 10.1021/JP201786H
Publisher: American Physical Society (APS)
Date: 09-11-2018
Publisher: American Chemical Society (ACS)
Date: 16-08-2022
Publisher: American Chemical Society (ACS)
Date: 23-12-2019
Publisher: Royal Society of Chemistry (RSC)
Date: 2013
DOI: 10.1039/C3DT32713B
Abstract: Density functional theory (DFT) has become the computational method of choice for modeling and characterization of carbon dioxide adsorbents, a broad family of materials which at present are urgently sought after for environmental applications. The description of polar carbon dioxide (CO(2)) molecules in low-coordinated environments like surfaces and porous materials, however, may be challenging for local and semi-local DFT approximations. Here, we present a thorough computational study in which the accuracy of DFT methods in describing the interactions of CO(2) with model alkali-earth-metal (AEM, Ca and Li) decorated carbon structures, namely anthracene (C(14)H(10)) molecules, is assessed. We find that gas-adsorption energies and equilibrium structures obtained with standard (i.e. LDA and GGA), hybrid (i.e. PBE0 and B3LYP) and van der Waals exchange-correlation functionals of DFT dramatically differ from the results obtained with second-order Møller-Plesset perturbation theory (MP2), an accurate computational quantum chemistry method. The major disagreements found can be mostly rationalized in terms of electron correlation errors that lead to wrong charge-transfer and electrostatic Coulomb interactions between CO(2) and AEM-decorated anthracene molecules. Nevertheless, we show that when the concentration of AEM atoms in anthracene is tuned to resemble as closely as possible the electronic structure of AEM-decorated graphene (i.e. an extended two-dimensional material), hybrid exchange-correlation DFT and MP2 methods quantitatively provide similar results.
Publisher: American Physical Society (APS)
Date: 10-05-2018
Publisher: Elsevier BV
Date: 09-2015
Publisher: Springer Science and Business Media LLC
Date: 03-10-2023
Publisher: IOP Publishing
Date: 30-03-2010
DOI: 10.1088/0953-8984/22/16/165402
Abstract: In a recent study we have reported a new type of trial wavefunction symmetric under the exchange of particles, which is able to describe a supersolid phase. In this work, we use the diffusion Monte Carlo method and this model wavefunction to study the properties of solid (4)He in two- and quasi-two-dimensional geometries. In the purely two-dimensional (2D) case, we obtain results for the total ground-state energy and freezing and melting densities which are in good agreement with previous exact Monte Carlo calculations performed with a slightly different interatomic potential model. We calculate the value of the zero-temperature superfluid fraction ρ(s)/ρ of 2D solid (4)He and find that it is negligible in all the considered cases, similarly to what is obtained in the perfect (free of defects) three-dimensional crystal using the same computational approach. Interestingly, by allowing the atoms to move locally in the direction perpendicular to the plane where they are confined to zero-point oscillations (quasi-2D crystal), we observe the emergence of a finite superfluid density that coexists with the periodicity of the system.
Publisher: American Chemical Society (ACS)
Date: 26-12-2020
DOI: 10.1021/ACS.NANOLETT.9B04727
Abstract: Conventional refrigeration methods based on compression-expansion cycles of greenhouse gases are environmentally threatening and cannot be miniaturized. Electrocaloric effects driven by electric fields are especially well suited for implementation of built-in cooling in portable electronic devices. However, most known electrocaloric materials present poor cooling performances near room temperature, contain toxic substances, and require high electric fields. Here, we show that lead-free ferroelectric thin-film bilayers composed of (Bi
Publisher: IOP Publishing
Date: 31-12-2018
Publisher: American Physical Society (APS)
Date: 30-01-2008
Publisher: Springer Science and Business Media LLC
Date: 08-10-2019
DOI: 10.1038/S41598-019-51037-8
Abstract: The high-pressure and high-temperature structural and chemical stability of ruthenium has been investigated via synchrotron X-ray diffraction using a resistively heated diamond anvil cell. In the present experiment, ruthenium remains stable in the hcp phase up to 150 GPa and 960 K. The thermal equation of state has been determined based upon the data collected following four different isotherms. A quasi-hydrostatic equation of state at ambient temperature has also been characterized up to 150 GPa. The measured equation of state and structural parameters have been compared to the results of ab initio simulations performed with several exchange-correlation functionals. The agreement between theory and experiments is generally quite good. Phonon calculations were also carried out to show that hcp ruthenium is not only structurally but also dynamically stable up to extreme pressures. These calculations also allow the pressure dependence of the Raman-active E 2 g mode and the silent B 1 g mode of Ru to be determined.
Publisher: Frontiers Media SA
Date: 08-08-2019
Publisher: American Chemical Society (ACS)
Date: 13-01-2023
Publisher: American Chemical Society (ACS)
Date: 27-10-2022
Publisher: American Chemical Society (ACS)
Date: 07-12-2021
Publisher: Springer Science and Business Media LLC
Date: 10-10-2010
Publisher: IOP Publishing
Date: 12-12-2008
Publisher: Springer Science and Business Media LLC
Date: 21-03-2012
Publisher: Wiley
Date: 06-11-2019
Abstract: Holey 2D metal oxides have shown great promise as functional materials for energy storage and catalysts. Despite impressive performance, their processing is challenged by the requirement of templates plus capping agents or high temperatures these materials also exhibit excessive thicknesses and low yields. The present work reports a metal-based coordination polymer (MCP) strategy to synthesize polycrystalline, holey, metal oxide (MO) nanosheets with thicknesses as low as two-unit cells. The process involves rapid exfoliation of bulk-layered, MCPs (Ce-, Ti-, Zr-based) into atomically thin MCPs at room temperature, followed by transformation into holey 2D MOs upon the removal of organic linkers in aqueous solution. Further, this work represents an extra step for decorating the holey nanosheets using precursors of transition metals to engineer their band alignments, establishing a route to optimize their photocatalysis. The work introduces a simple, high-yield, room-temperature, and template-free approach to synthesize ultrathin holey nanosheets with high-level functionalities.
Publisher: American Physical Society (APS)
Date: 03-08-2017
Publisher: American Physical Society (APS)
Date: 03-2022
Publisher: Royal Society of Chemistry (RSC)
Date: 2023
DOI: 10.1039/D2MH01516A
Abstract: A comprehensive first-principles database is introduced for prototypical families of inorganic solid-state electrolytes containing sets of zero-temperature DFT and finite-temperature ab initio molecular dynamic results.
Publisher: American Physical Society (APS)
Date: 04-01-2012
Publisher: American Physical Society (APS)
Date: 04-12-2014
Publisher: Springer Science and Business Media LLC
Date: 16-11-2012
Publisher: Wiley
Date: 31-05-2021
Abstract: Control over the fabrication of state‐of‐the‐art portable pseudocapacitors with the desired transparency, mechanical flexibility, capacitance, and durability is challenging, but if resolved will have fundamental implications. Here, defect‐rich Mn 1− x − y (Ce x La y )O 2−δ ultrathin films with controllable thicknesses (5–627 nm) and transmittance (≈29–100%) are fabricated via an electrochemical chrono erometric deposition using a aqueous precursor derived from end‐of‐life nickel‐metal hydride batteries. Due to percolation impacts on the optoelectronic properties of ultrathin films, a representative Mn 1− x − y (Ce x La y )O 2−δ film with 86% transmittance exhibits an outstanding areal capacitance of 3.4 mF cm −2 , mainly attributed to the intercalation/de‐intercalation of anionic O 2− through the atomic tunnels of the stratified Mn 1− x − y (Ce x La y )O 2−δ crystallites. Furthermore, the Mn 1− x − y (Ce x La y )O 2−δ thin‐film device exhibits excellent capacitance retention of ≈90% after 16 000 cycles. Such stability is associated with intervalence charge transfer occurring among interstitial Ce/La cations and Mn oxidation states within the Mn 1− x − y (Ce x La y )O 2−δ structure. The energy and power densities of the transparent flexible Mn 1− x − y (Ce x La y )O 2−δ full‐cell pseudocapacitor device, is measured to be 0.088 μWh cm −2 and 843 µW cm −2 , respectively. These values show insignificant changes under vigorous twisting and bending to 45–180° confirming these value‐added materials are intriguing alternatives for size‐sensitive energy storage devices.
Publisher: Wiley
Date: 28-09-2021
Abstract: Perovskite oxides are regarded as promising electrocatalysts for water splitting due to their cost‐effectiveness, high efficiency and durability in the oxygen evolution reaction (OER). Despite these advantages, a fundamental understanding of how critical structural parameters of perovskite electrocatalysts influence their activity and stability is lacking. Here, we investigate the impact of structural defects on OER performance for representative LaNiO 3 perovskite electrocatalysts. Hydrogen reduction of 700 °C calcined LaNiO 3 induces a high density of surface oxygen vacancies, and confers significantly enhanced OER activity and stability compared to unreduced LaNiO 3 the former exhibit a low onset overpotential of 380 mV at 10 mA cm −2 and a small Tafel slope of 70.8 mV dec −1 . Oxygen vacancy formation is accompanied by mixed Ni 2+ /Ni 3+ valence states, which quantum‐chemical DFT calculations reveal modify the perovskite electronic structure. Further, it reveals that the formation of oxygen vacancies is thermodynamically more favourable on the surface than in the bulk it increases the electronic conductivity of reduced LaNiO 3 in accordance with the enhanced OER activity that is observed.
Publisher: American Physical Society (APS)
Date: 04-06-2008
Publisher: Elsevier BV
Date: 12-2022
DOI: 10.1016/J.JCIS.2022.08.061
Abstract: Ni-rich layered oxides, such as LiNi
Publisher: World Scientific Pub Co Pte Lt
Date: 20-12-2006
DOI: 10.1142/S0217979206036211
Abstract: We present a diffusion Monte Carlo simulation of metastable superfluid 4 He at zero temperature and pressures beyond freezing (~ 25 bar) up to 275 bar. The equation of state of liquid 4 He is extended to the overpressurized regime, where the pressure dependence of the static structure factor and the condensate fraction is obtained. Along this large pressure range, excited-state energy corresponding to the roton has been determined using the release-node technique. Our results show that both the roton energies and the condensate fraction decrease with increasing pressure but do not become zero. We compare our calculations to recent experimental data in overpressurized regime.
Publisher: Royal Society of Chemistry (RSC)
Date: 2021
DOI: 10.1039/D1TA06473H
Abstract: This work reports fabrication of centimetre-size, flexible, self-adhesive ZnO-based heterojunction patches with a tuned electronic band and outstanding electrochemical activity, offering promising alternatives for noble electrocatalysts such as Pt.
Publisher: American Physical Society (APS)
Date: 17-03-2011
Publisher: American Physical Society (APS)
Date: 03-01-2023
Publisher: American Physical Society (APS)
Date: 10-08-2009
Publisher: IOP Publishing
Date: 07-2008
Publisher: American Physical Society (APS)
Date: 03-12-2013
Publisher: American Physical Society (APS)
Date: 13-11-2018
Publisher: American Physical Society (APS)
Date: 30-12-2013
Publisher: Royal Society of Chemistry (RSC)
Date: 2023
DOI: 10.1039/D3CP02318D
Publisher: American Physical Society (APS)
Date: 05-06-2007
Publisher: American Chemical Society (ACS)
Date: 09-01-2017
Publisher: AIP Publishing
Date: 12-2019
DOI: 10.1063/1.5113620
Abstract: Current refrigeration technologies based on compression cycles of greenhouse gases are environmentally threatening and cannot be scaled down to on-chip dimensions. Solid-state cooling is an environmentally friendly and highly scalable technology that may solve most of the problems associated with current refrigerant methods. Solid-state cooling consists of applying external fields (magnetic, electric, and mechanical) on caloric materials, which react thermally as a result of induced phase transformations. From an energy efficiency point of view, mechanocaloric compounds, in which the phase transitions of interest are driven by mechanical stresses, probably represent the most encouraging type of caloric materials. Conventional mechanocaloric materials like shape-memory alloys already display good cooling performances however, in most cases they also present critical mechanical fatigue and hysteresis problems that limit their applicability. Finding new mechanocaloric materials and mechanisms that are able to overcome those problems, while simultaneously rendering large temperature shifts, is necessary to further advance the field of solid-state cooling. In this article, we review novel families of mechanocaloric materials that in recent years have been shown to be especially promising in the aspects that conventional mechanocaloric materials are not, and that exhibit unconventional but significant caloric effects. We emphasize elastocaloric materials, in which the targeted cooling spans are obtained through uniaxial stresses, since from an applied perspective they appear to be the most accomplished ones. Two different types of mechanocaloric materials emerge as particularly hopeful from our analysis: (1) compounds that exhibit field-induced order-disorder phase transitions involving either ions or molecules (polymers, fast-ion conductors, and plastic crystals), and (2) multiferroics in which the structural parameters are strongly coupled with the polar and/or magnetic degrees of freedom (magnetic alloys and oxide perovskites).
Publisher: American Physical Society (APS)
Date: 08-10-2008
Publisher: Elsevier BV
Date: 02-2018
DOI: 10.1016/J.JCIS.2017.10.113
Abstract: Resistive switching behaviour can be classified into digital and analog switching based on its abrupt and gradual resistance change characteristics. Realizing the transition from digital to analog switching in the same device is essential for understanding and controlling the performance of the devices with various switching mechanisms. Here, we investigate the resistive switching in a device made with strontium titanate (SrTiO
Publisher: American Physical Society (APS)
Date: 23-02-2012
Publisher: Royal Society of Chemistry (RSC)
Date: 2012
DOI: 10.1039/C2JM33811D
Publisher: Springer Science and Business Media LLC
Date: 06-2021
DOI: 10.1038/S41598-021-91018-4
Abstract: Epitaxially grown $$\\hbox {SrTiO}_{{3}}$$ SrTiO 3 (STO) thin films are material enablers for a number of critical energy-conversion and information-storage technologies like electrochemical electrode coatings, solid oxide fuel cells and random access memories. Oxygen vacancies ( $${\\mathrm{V}_{{\\mathrm{O}}}}$$ V O ), on the other hand, are key defects to understand and tailor many of the unique functionalities realized in oxide perovskite thin films. Here, we present a comprehensive and technically sound ab initio description of $${\\mathrm{V}_{{\\mathrm{O}}}}$$ V O in epitaxially strained (001) STO thin films. The novelty of our first-principles study lies in the incorporation of lattice thermal excitations on the formation energy and diffusion properties of $${\\mathrm{V}_{{\\mathrm{O}}}}$$ V O over wide epitaxial strain conditions ( $$-4 \\le \\eta \\le +4$$ - 4 ≤ η ≤ + 4 %). We found that thermal lattice excitations are necessary to obtain a satisfactory agreement between first-principles calculations and the available experimental data for the formation energy of $${\\mathrm{V}_{{\\mathrm{O}}}}$$ V O . Furthermore, it is shown that thermal lattice excitations noticeably affect the energy barriers for oxygen ion diffusion, which strongly depend on $$\\eta $$ η and are significantly reduced (increased) under tensile (compressive) strain. The present work demonstrates that for a realistic theoretical description of oxygen vacancies in STO thin films is necessary to consider lattice thermal excitations, thus going beyond standard zero-temperature ab initio approaches.
Publisher: American Chemical Society (ACS)
Date: 19-07-2019
Publisher: Wiley
Date: 09-2022
Publisher: Elsevier BV
Date: 10-2018
Publisher: American Chemical Society (ACS)
Date: 04-10-2021
Publisher: Springer Science and Business Media LLC
Date: 07-06-2021
DOI: 10.1038/S41598-021-91123-4
Abstract: Traditional refrigeration technologies based on compression cycles of greenhouse gases pose serious threats to the environment and cannot be downscaled to electronic device dimensions. Solid-state cooling exploits the thermal response of caloric materials to changes in the applied external fields (i.e., magnetic, electric and/or mechanical stress) and represents a promising alternative to current refrigeration methods. However, most of the caloric materials known to date present relatively small adiabatic temperature changes ( $$|\Delta T| \sim 1$$ | Δ T | ∼ 1 to 10 K) and/or limiting irreversibility issues resulting from significant phase-transition hysteresis. Here, we predict by using molecular dynamics simulations the existence of colossal barocaloric effects induced by pressure (isothermal entropy changes of $$|\Delta S| \sim 100$$ | Δ S | ∼ 100 J K $$^{-1}$$ - 1 kg $$^{-1}$$ - 1 ) in the energy material Li $$_{2}$$ 2 B $$_{12}$$ 12 H $$_{12}$$ 12 . Specifically, we estimate $$|\Delta S| = 367$$ | Δ S | = 367 J K $$^{-1}$$ - 1 kg $$^{-1}$$ - 1 and $$|\Delta T| = 43$$ | Δ T | = 43 K for a small pressure shift of P = 0.1 GPa at $$T = 480$$ T = 480 K. The disclosed colossal barocaloric effects are originated by a fairly reversible order–disorder phase transformation involving coexistence of Li $$^{+}$$ + diffusion and (BH) $$_{12}^{-2}$$ 12 - 2 reorientational motion at high temperatures.
Publisher: Wiley
Date: 09-02-2020
Publisher: Springer Science and Business Media LLC
Date: 05-06-2020
DOI: 10.1038/S41524-020-0344-3
Abstract: Multiferroics in which giant ferroelectric polarization and magnetism coexist are of tremendous potential for engineering disruptive applications in information storage and energy conversion. Yet the functional properties of multiferroics are thought to be affected detrimentally by the presence of point defects, which may be abundant due to the volatile nature of some constituent atoms and the high temperatures involved in the synthesis of materials. Here, we demonstrate with theoretical methods that oxygen vacancies may enhance the functionality of multiferroics by radically changing their magnetic interactions in thin films. Specifically, oxygen vacancies may restore missing magnetic super-exchange interactions in large axial ratio phases, leading to full antiferromagnetic spin ordering, and induce the stabilization of ferrimagnetic states with considerable net magnetizations. Our theoretical study should help to clarify the origins of long-standing controversies in bismuth ferrite and improve the design of technological applications based on multiferroics.
Publisher: American Physical Society (APS)
Date: 31-12-2015
Publisher: Royal Society of Chemistry (RSC)
Date: 2021
DOI: 10.1039/D0NR08097G
Abstract: The present work reports a template-free approach to fabricate 3D mesoporous CeO 2−x -based heterojunction nanostructures comprised of holey 2D nanosheets with outstanding densities of active sites that deliver excellent CO conversion performance.
Publisher: American Physical Society (APS)
Date: 28-06-2013
Publisher: American Chemical Society (ACS)
Date: 28-12-2022
Publisher: IOP Publishing
Date: 16-10-2013
DOI: 10.1088/0953-8984/25/44/445011
Abstract: We determined the zero-temperature phase diagram of D₂ physisorbed on graphane using the diffusion Monte Carlo method. The substrate used was C-graphane, an allotropic form of the compound that has been experimentally obtained through hydrogenation of graphene. We found that the ground state is the δ phase, a commensurate structure observed experimentally when D₂ is adsorbed on graphite, and not the registered √3 x √3 structure characteristic of H₂ on the same substrate.
Publisher: Elsevier BV
Date: 2016
Publisher: Wiley
Date: 04-07-2022
Abstract: Ruddlesden–Popper phase 2D perovskite solar cells (PSCs) exhibit improved lifetime while still facing challenges such as phase alignment and up‐scaling to module‐level devices. Herein, polyelectrolytes are explored to tackle this issue. The contact between perovskite and hole‐transport layer (HTL) is important for decreasing interfacial non‐radiative recombination and scalable fabrication of uniform 2D perovskite films. Through exploring compatible butylamine cations, we first demonstrate poly(3‐(4‐carboxybutyl)thiophene‐2,5‐diyl)‐butylamine (P3CT‐BA) as an efficient HTL for 2D PSCs due to its great hydrophilicity, relatively high hole mobility and uniform surface. More importantly, the tailored P3CT‐BA has an anchoring effect and acts as the buried passivator for 2D perovskites. Consequently, a best efficiency approaching 18 % was achieved and we further first report large‐area (2×3 cm 2 , 5×5 cm 2 ) 2D perovskite minimodules with an impressive efficiency of 14.81 % and 11.13 %, respectively.
Publisher: American Chemical Society (ACS)
Date: 14-04-2016
DOI: 10.1021/ACS.NANOLETT.6B00422
Abstract: Mechanocaloric materials experience a change in temperature when a mechanical stress is applied on them adiabatically. Thus, far, only ferroelectrics and superelastic metallic alloys have been considered as potential mechanocaloric compounds to be exploited in solid-state cooling applications. Here we show that giant mechanocaloric effects occur in hitherto overlooked fast ion conductors (FIC), a class of multicomponent materials in which above a critical temperature, Ts, a constituent ionic species undergoes a sudden increase in mobility. Using first-principles and molecular dynamics simulations, we found that the superionic transition in fluorite-structured FIC, which is characterized by a large entropy increase of the order of 10(2) JK(-1) kg(-1), can be externally tuned with hydrostatic, biaxial, or uniaxial stresses. In particular, Ts can be reduced several hundreds of degrees through the application of moderate tensile stresses due to the concomitant drop in the formation energy of Frenkel pair defects. We predict that the adiabatic temperature change in CaF2 and PbF2, two archetypal fluorite-structured FIC, close to their critical points are of the order of 10(2) and 10(1) K, respectively. This work advocates that FIC constitute a new family of mechanocaloric materials showing great promise for prospective solid-state refrigeration applications.
Publisher: American Chemical Society (ACS)
Date: 05-08-2022
Abstract: Lithium-rich manganese-based oxides (LRMO) are regarded as promising cathode materials for powering electric applications due to their high capacity (250 mAh g
Publisher: Wiley
Date: 10-01-2019
Publisher: Elsevier BV
Date: 04-2022
Publisher: American Physical Society (APS)
Date: 11-12-2014
Publisher: Wiley
Date: 06-12-2017
Publisher: Elsevier BV
Date: 2020
DOI: 10.2139/SSRN.3716044
Publisher: Wiley
Date: 06-05-2019
Publisher: Springer Science and Business Media LLC
Date: 2004
Publisher: Elsevier BV
Date: 08-2021
Publisher: American Chemical Society (ACS)
Date: 05-01-2018
Publisher: IOP Publishing
Date: 08-09-2016
DOI: 10.1088/0953-8984/28/44/445401
Abstract: We present a combined theoretical and experimental study of the high-pressure behavior of thallium. X-ray diffraction experiments have been carried out at room temperature (RT) up to 125 GPa using diamond-anvil cells (DACs), nearly doubling the pressure range of previous experiments. We have confirmed the hcp-fcc transition at 3.5 GPa and determined that the fcc structure remains stable up to the highest pressure attained in the experiments. In addition, HP-HT experiments have been performed up to 8 GPa and 700 K by using a combination of XRD and a resistively heated DAC. Information on the phase boundaries is obtained, as well as crystallographic information on the HT bcc phase. The equation of state (EOS) for different phases is reported. Ab initio calculations have also been carried out considering several potential high-pressure structures. They are consistent with the experimental results and predict that, among the structures considered in the calculations, the fcc structure of thallium is stable up to 4.3 TPa. Calculations also predict the post-fcc phase to have a close-packed orthorhombic structure above 4.3 TPa.
Publisher: American Physical Society (APS)
Date: 09-09-2020
Publisher: Elsevier BV
Date: 07-2021
Publisher: Royal Society of Chemistry (RSC)
Date: 2020
DOI: 10.1039/C9CP05939C
Abstract: Thermoelectric materials can be used to harvest waste heat into electricity and in thermal management applications. A new family of Li-based fast-ion conductors are shown to be promising thermoelectric materials.
Publisher: Springer Science and Business Media LLC
Date: 13-06-2019
DOI: 10.1038/S41467-019-10621-2
Abstract: Two-dimensional metal oxide pseudocapacitors are promising candidates for size-sensitive applications. However, they exhibit limited energy densities and inferior power densities. Here, we present an electrodeposition technique by which ultrathin CeO 2− x films with controllable volumetric oxygen vacancy concentrations can be produced. This technique offers a layer-by-layer fabrication route for ultrathin CeO 2− x films that render Ce 3+ concentrations as high as ~60 at% and a volumetric capacitance of 1873 F cm −3 , which is among the highest reported to the best of our knowledge. This exceptional behaviour originates from both volumetric oxygen vacancies, which enhance electron conduction, and intercrystallite water, which promotes proton conduction. Consequently, simultaneous charging on the surface and in the bulk occur, leading to the observation of redox pseudocapacitive behaviour in CeO 2− x . Thermodynamic investigations reveal that the energy required for oxygen vacancy formation can be reduced significantly by proton-assisted reactions. This cyclic deposition technique represents an efficient method to fabricate metal oxides of precisely controlled defect concentrations and thicknesses.
Publisher: Royal Society of Chemistry (RSC)
Date: 2023
DOI: 10.1039/D3EE00770G
Abstract: Illustration of protein-based MEG generating electricity by absorbing water from moisture.
Publisher: American Chemical Society (ACS)
Date: 24-10-2017
Abstract: Finding solid-state electrolytes with high ionic conductivity near room temperature is an important prerequisite for developing all-solid-state electrochemical batteries. Here, we investigate the effects of point defects (vacancies) and biaxial stress on the superionic properties of fast-ion conductors (represented by the archetypal compounds CaF
Publisher: Springer Science and Business Media LLC
Date: 25-07-2023
DOI: 10.1038/S41467-023-40240-X
Abstract: Helium, the second most abundant element in the universe, exhibits an extremely large electronic band gap of about 20 eV at ambient pressures. While the metallization pressure of helium has been accurately determined, thus far little attention has been paid to the specific mechanisms driving the band-gap closure and electronic properties of this quantum crystal in the terapascal regime (1 TPa = 10 Mbar). Here, we employ density functional theory and many-body perturbation calculations to fill up this knowledge gap. It is found that prior to reaching metallicity helium becomes an excitonic insulator (EI), an exotic state of matter in which electrostatically bound electron-hole pairs may form spontaneously. Furthermore, we predict metallic helium to be a superconductor with a critical temperature of ≈ 20 K just above its metallization pressure and of ≈ 70 K at 100 TPa. These unforeseen phenomena may be critical for improving our fundamental understanding and modeling of celestial bodies.
Publisher: MDPI AG
Date: 29-01-2018
DOI: 10.3390/CRYST8020064
Publisher: Royal Society of Chemistry (RSC)
Date: 2021
DOI: 10.1039/D0TC04304D
Abstract: Compositional engineering of BiFeO 3 can significantly boost its optoelectronic properties.
Publisher: Springer Science and Business Media LLC
Date: 22-04-2020
DOI: 10.1038/S41598-020-63865-0
Abstract: An amendment to this paper has been published and can be accessed via a link at the top of the paper.
Publisher: American Chemical Society (ACS)
Date: 03-01-2019
DOI: 10.26434/CHEMRXIV.6388637.V3
Abstract: Boron nitride (BN) is a material with outstanding technological promise because of its exceptional thermochemical stability, structural, electronic and thermal conductivity properties, and extreme hardness. Yet, the relative thermodynamic stability of its most common polymorphs (diamond-like cubic and graphite-like hexagonal) has not been resolved satisfactorily because of the crucial role played by kinetic factors in the formation of BN phases at high temperatures and pressures (experiments), and by competing bonding, electrostatic and many-body dispersion forces in BN cohesion (theory). This lack of understanding h ers the development of potential technological applications, and challenges the boundaries of fundamental science. Here, we use high-level first-principles theories that correctly reproduce all important electronic interactions (the adiabatic-connection fluctuation-dissipation theorem in the random phase approximation) to estimate with unprecedented accuracy the energy differences between BN polymorphs, and thus overcome the accuracy hurdle that hindered previous theoretical studies. We show that the ground-state phase of BN is cubic and that the frequently observed two-dimensional hexagonal polymorph becomes entropically stabilized over the cubic at temperatures slightly above ambient conditions (Tc = 63+-20'C). We also reveal a new low-symmetry monoclinic phase that is extremely competitive with the other low-energy polymorphs and which could explain the origins of the experimentally observed ``compressed h--BN'' phase. Our theoretical findings therefore should stimulate new experimental efforts in bulk BN as well as promote the use of high-level theories in modelling of technologically relevant van der Waals materials.
Publisher: Elsevier BV
Date: 06-2022
Publisher: American Chemical Society (ACS)
Date: 06-2210
DOI: 10.1021/JP3014805
Publisher: American Chemical Society (ACS)
Date: 06-12-2022
Publisher: American Chemical Society (ACS)
Date: 04-2022
Abstract: Metallic 1T-phase MoS
Publisher: Wiley
Date: 02-12-2022
Abstract: Interfacial thermal transport plays a prominent role in the thermal management of nanoscale objects and is of fundamental importance for basic research and nanodevices. At metal/insulator interfaces, a configuration commonly found in electronic devices, heat transport strongly depends upon the effective energy transfer from thermalized electrons in the metal to the phonons in the insulator. However, the mechanism of interfacial electron-phonon coupling and thermal transport at metal/insulator interfaces is not well understood. Here, the observation of a substantial enhancement of the interfacial thermal resistance and the important role of surface charges at the metal/ferroelectric interface in an Al/BiFeO
Publisher: Springer Science and Business Media LLC
Date: 29-11-2017
DOI: 10.1038/S41467-017-01898-2
Abstract: Current interest in barocaloric effects has been stimulated by the discovery that these pressure-driven thermal changes can be giant near ferroic phase transitions in materials that display magnetic or electrical order. Here we demonstrate giant inverse barocaloric effects in the solid electrolyte AgI, near its superionic phase transition at ~420 K. Over a wide range of temperatures, hydrostatic pressure changes of 2.5 kbar yield large and reversible barocaloric effects, resulting in large values of refrigerant capacity. Moreover, the peak values of isothermal entropy change (60 J K −1 kg −1 or 0.34 J K −1 cm −3 ) and adiabatic temperature changes (18 K), which we identify for a starting temperature of 390 K, exceed all values previously recorded for barocaloric materials. Our work should therefore inspire the study of barocaloric effects in a wide range of solid electrolytes, as well as the parallel development of cooling devices.
Publisher: American Physical Society (APS)
Date: 28-03-2019
Publisher: Royal Society of Chemistry (RSC)
Date: 2023
DOI: 10.1039/D3TA02565A
Abstract: Our study highlights importance elements of the nanoscale intragrain feature that may pave the way to high-efficiency perovskite solar cells.
Publisher: American Association for the Advancement of Science (AAAS)
Date: 04-01-2019
Abstract: High-level many-body ab initio calculations reveal a strong phase competition in boron nitride near-ambient conditions.
Publisher: Royal Society of Chemistry (RSC)
Date: 2020
DOI: 10.1039/D0TA03470C
Abstract: Enhanced OER performance of Ni(Fe) hydroxide through UV/ozone treatment.
Publisher: Informa UK Limited
Date: 12-2008
Publisher: American Chemical Society (ACS)
Date: 09-07-2020
Publisher: Springer Science and Business Media LLC
Date: 03-2019
Publisher: American Physical Society (APS)
Date: 29-01-2020
Publisher: American Physical Society (APS)
Date: 28-10-2010
Publisher: American Chemical Society (ACS)
Date: 20-05-2013
DOI: 10.1021/JP401577J
Publisher: Wiley
Date: 22-04-2022
Abstract: Organic–inorganic hybrid lead halide perovskite solar cells have made unprecedented progress in improving photovoltaic efficiency during the past decade, while still facing critical stability challenges. Herein, the natural organic dye Indigo is explored for the first time to be an efficient molecular passivator that assists in the preparation of high‐quality hybrid perovskite film with reduced defects and enhanced stability. The Indigo molecule with both carbonyl and amino groups can provide bifunctional chemical passivation for defects. In‐depth theoretical and experimental studies show that the Indigo molecules firmly binds to the perovskite surfaces, enhancing the crystallization of perovskite films with improved morphology. Consequently, the Indigo‐passivated perovskite film exhibits increased grain size with better uniformity, reduced grain boundaries, lowered defect density, and retarded ion migration, boosting the device efficiency up to 23.22%, and ≈21% for large‐area device (1 cm 2 ). Furthermore, the Indigo passivation can enhance device stability in terms of both humidity and thermal stress. These results provide not only new insights into the multipassivation role of natural organic dyes but also a simple and low‐cost strategy to prepare high‐quality hybrid perovskite films for optoelectronic applications based on Indigo derivatives.
Publisher: Wiley
Date: 11-06-2022
Abstract: Introducing large oxygen deficiencies while retaining low resistivity is important for enhancing the overall thermoelectric properties in 3d transition‐metal oxides. In this study, a new synthesis route to reconstruct the insulating brownmillerite SrCoO 2.5 is adapted. Through a step‐by‐step nano‐blocks modification, a series of highly‐conductive layered structures is evolved, which are [Sr 2 O 2 H 2 ] 0.5 CoO 2 , [Sr 2 O 2 ] 0.4 CoO 2 , and [Sr 2 CoO 3 ] 0.57 CoO 2 , while still retaining considerable Seebeck coefficient ( ≈ 100 µ V K −1 ). Coexistence of low resistivity and high oxygen deficiency is realized in the latter two polymorphs by forming a majority of sintered oxygen vacancies in the rock‐salt layer and a minority of normal oxygen vacancies in the CoO 2 layer. A room‐temperature in‐plane power factor of 3.6 mW K −2 m −1 , power output density of 4.5 W m −2 at a temperature difference of 28 K, and an out‐of‐plane thermal conductivity of 0.33 W K −1 m −1 are obtained in the [Sr 2 O 2 ] 0.4 CoO 2 thin film that exhibits the highest oxygen deficiency (δ = 2.95), which is on par with Bi 2 Te 3 , the benchmark. It is pointed out that proper distribution of oxygen vacancy is essential in tailoring the physical and chemical properties of transition‐metal oxides. The sintered/normal oxygen vacancy layer model provides guidance to the exploration of materials with both low electric resistivity and thermal conductivity.
Publisher: American Chemical Society (ACS)
Date: 24-02-2021
Publisher: American Physical Society (APS)
Date: 19-06-2006
Publisher: American Physical Society (APS)
Date: 21-07-2014
Publisher: Elsevier BV
Date: 2015
Publisher: AIP Publishing
Date: 16-05-2007
DOI: 10.1063/1.2735324
Abstract: Ab initio calculations of the melting curve of molybdenum for the pressure range 0–400 GPa are reported. The calculations employ density functional theory (DFT) with the Perdew-Burke-Ernzerhof exchange-correlation functional in the projector augmented wave (PAW) implementation. Tests are presented showing that these techniques accurately reproduce experimental data on low-temperature body-centered cubic (bcc) Mo, and that PAW agrees closely with results from the full-potential linearized augmented plane-wave implementation. The work attempts to overcome the uncertainties inherent in earlier DFT calculations of the melting curve of Mo, by using the “reference coexistence” technique to determine the melting curve. In this technique, an empirical reference model (here, the embedded-atom model) is accurately fitted to DFT molecular dynamics data on the liquid and the high-temperature solid, the melting curve of the reference model is determined by simulations of coexisting solid and liquid, and the ab initio melting curve is obtained by applying free-energy corrections. The calculated melting curve agrees well with experiment at ambient pressure and is consistent with shock data at high pressure, but does not agree with the high-pressure melting curve deduced from static compression experiments. Calculated results for the radial distribution function show that the short-range atomic order of the liquid is very similar to that of the high-T solid, with a slight decrease of coordination number on passing from solid to liquid. The electronic densities of states in the two phases show only small differences. The results do not support a recent theory according to which very low dTm∕dP values are expected for bcc transition metals because of electron redistribution between s-p and d states.
Publisher: Elsevier BV
Date: 03-2021
Publisher: Elsevier BV
Date: 2021
DOI: 10.2139/SSRN.3774576
Publisher: American Association for the Advancement of Science (AAAS)
Date: 02-06-2017
Abstract: A perovskite oxide is predicted to present a double-reentrant phase transition sequence driven by spin-phonon couplings.
Publisher: Royal Society of Chemistry (RSC)
Date: 2022
DOI: 10.1039/D2TA05941J
Abstract: A high-throughput screening of piezo-photocatalytic materials based on first-principles calculations and a simple electrostatic model is presented that identifies new bulk compounds able to catalyse the water splitting reaction under sunlight.
Publisher: American Chemical Society (ACS)
Date: 06-12-2021
Publisher: Springer Science and Business Media LLC
Date: 08-12-2021
DOI: 10.1038/S41524-021-00671-W
Abstract: Lead zirconate (PbZrO 3 ) is considered the prototypical antiferroelectric material with an antipolar ground state. Yet, several experimental and theoretical works hint at a partially polar behaviour in this compound, indicating that the polarization may not be completely compensated. In this work, we propose a simple ferrielectric structure for lead zirconate. First-principles calculations reveal this state to be more stable than the commonly accepted antiferroelectric phase at low temperatures, possibly up to room temperature, suggesting that PbZrO 3 may not be antiferroelectric at ambient conditions. We discuss the implications of our discovery, how it can be reconciled with experimental observations and how the ferrielectric phase could be obtained in practice.
Publisher: Elsevier BV
Date: 06-2020
Publisher: Royal Society of Chemistry (RSC)
Date: 2020
DOI: 10.1039/C9NR08604H
Abstract: Experimental data for Ce-doped TiO 2 are interpreted through solubility mechanisms, structural analogies, defect energies, and a new defect equilibria formalism.
Publisher: Springer Science and Business Media LLC
Date: 09-10-2014
Publisher: AIP Publishing
Date: 04-05-2009
DOI: 10.1063/1.3126683
Abstract: We present calculations of the free energy, and hence the melting properties, of a simple tight-binding model for transition metals in the region of d-band filling near the middle of a d-series, the parameters of the model being designed to mimic molybdenum. The melting properties are calculated for pressures ranging from ambient to several megabars. The model is intended to be the simplest possible tight-binding representation of the two basic parts of the energy: first, the pairwise repulsion due to Fermi exclusion and second, the d-band bonding energy described in terms of an electronic density of states that depends on structure. In addition to the number of d-electrons, the model contains four parameters, which are adjusted to fit the pressure dependent d-band-width and the zero-temperature pressure-volume relation of Mo. We show that the resulting model reproduces well the phonon dispersion relations of Mo in the body-centered-cubic structure, as well as the radial distribution function of the high-temperature solid and liquid given by earlier first-principles simulations. Our free energy calculations start from the free energy of the liquid and solid phases of the purely repulsive pair potential model, without d-band bonding. The free energy of the full tight-binding model is obtained from this by thermodynamic integration. The resulting melting properties of the model are quite close to those given by earlier first-principles work on Mo. An interpretation of these melting properties is provided by showing how they are related to those of the purely repulsive model.
Publisher: American Physical Society (APS)
Date: 04-11-2010
Publisher: Wiley
Date: 28-04-2022
Abstract: Hybrid halide perovskites have emerged as highly promising photovoltaic materials because of their exceptional optoelectronic properties, which are often optimized via compositional engineering like mixing halides. It is well established that hybrid perovskites undergo a series of structural phase transitions as temperature varies. In this work, the authors find that phase transitions are substantially suppressed in mixed‐halide hybrid perovskite single crystals of MAPbI 3‐x Br x (MA = CH 3 NH 3 + and x = 1 or 2) using a complementary suite of diffraction and spectroscopic techniques. Furthermore, as a general behavior, multiple crystallographic phases coexist in mixed‐halide perovskites over a wide temperature range, and a slightly distorted monoclinic phase, hitherto unreported for hybrid perovskites, is dominant at temperatures above 100 K. The anomalous structural evolution is correlated with the glassy behavior of organic cations and optical phonons in mixed‐halide perovskites. This work demonstrates the complex interplay between composition engineering and lattice dynamics in hybrid perovskites, shedding new light on their unique properties.
Publisher: American Physical Society (APS)
Date: 16-12-2021
Publisher: Royal Society of Chemistry (RSC)
Date: 2021
DOI: 10.1039/D0MH00654H
Abstract: The present work provides a comprehensive array of design parameters for the fabrication of the principal morphologies of nanoceria.
Publisher: IOP Publishing
Date: 26-01-2009
Publisher: Springer Science and Business Media LLC
Date: 06-2005
Publisher: Springer Science and Business Media LLC
Date: 20-08-2018
DOI: 10.1038/S41467-018-05835-9
Abstract: Mechanocaloric materials undergo sizable temperature changes during stress-induced phase transformations and hence are highly sought after for solid-state cooling applications. Most known mechanocaloric materials, however, operate at non-ambient temperatures and involve first-order structural transitions that pose practical cyclability issues. Here, we demonstrate large room-temperature mechanocaloric effects in the absence of any structural phase transformation in the fast-ion conductor Li 3 N (|Δ S | ~ 25 J K −1 kg −1 and |Δ T | ~ 5 K). Depending on whether the applied stress is hydrostatic or uniaxial the resulting caloric effect is either direct (Δ T 0) or inverse (Δ T 0). The dual caloric response of Li 3 N is due exclusively to stress-induced variations on its ionic conductivity, which entail large entropy and volume changes that are fully reversible. Our work should motivate the search of large and dual mechanocaloric effects in a wide variety of superionic materials already employed in electrochemical devices.
Publisher: IOP Publishing
Date: 07-2008
Publisher: Springer Science and Business Media LLC
Date: 20-09-2021
DOI: 10.1038/S41598-021-97973-2
Abstract: Disorder–disorder phase transitions are rare in nature. Here, we present a comprehensive low-temperature experimental and theoretical study of the heat capacity and vibrational density of states of 1-fluoro-adamantane (C 10 H 15 F), an intriguing molecular crystal that presents a continuous disorder–disorder phase transition at T = 180 K and a low-temperature tetragonal phase that exhibits fractional fluorine occupancy. It is shown that fluorine occupancy disorder in the low- T phase of 1-fluoro-adamantane gives rise to the appearance of low-temperature glassy features in the corresponding specific heat (i.e., “boson peak” -BP-) and vibrational density of states. We identify the inflation of low-energy optical modes as the main responsible for the appearance of such glassy heat-capacity features and propose a straightforward correlation between the first localized optical mode and maximum BP temperature for disordered molecular crystals (either occupational or orientational). Thus, the present study provides new physical insights into the possible origins of the BP appearing in disordered materials and expands the set of molecular crystals in which “glassy-like” heat-capacity features have been observed.
Publisher: Wiley
Date: 11-05-2020
Publisher: American Physical Society (APS)
Date: 27-04-2017
Publisher: American Physical Society (APS)
Date: 14-12-2015
Publisher: Elsevier BV
Date: 09-2010
Publisher: Wiley
Date: 26-06-2019
Publisher: Wiley
Date: 29-09-2021
Abstract: Protonated 3d transition‐metal oxides often display low electronic conduction, which h ers their application in electric, magnetic, thermoelectric, and catalytic fields. Electronic conduction can be enhanced by co‐inserting oxygen acceptors simultaneously. However, the currently used redox approaches hinder protons and oxygen ions co‐insertion due to the selective switching issues. Here, a thermal hydration strategy for systematically exploring the synthesis of conductive protonated oxides from 3d transition‐metal oxides is introduced. This strategy is illustrated by synthesizing a novel layered‐oxide SrCoO 3 H from the brownmillerite SrCoO 2.5 . Compared to the insulating SrCoO 2.5 , SrCoO 3 H exhibits an unprecedented high electronic conductivity above room temperature, water uptake at 250 °C, and a thermoelectric power factor of up to 1.2 mW K −2 m −1 at 300 K. These findings open up opportunities for creating high‐conductive protonated layered oxides by protons and oxygen ions co‐doping.
Publisher: Wiley
Date: 27-10-2022
Abstract: All‐inorganic CsPbX 3 (X = Cl, Br, I, or mixed halides) perovskite quantum dots (QDs) exhibit tunable optical bandgaps and narrow emission peaks, which have received worldwide interest in the field of both photovoltaics (PVs) and light‐emitting diodes (LEDs). Herein, it is reported a discovery that CsPbI 3 perovskite QD solar cell can simultaneously deliver high PV performance and intense electroluminescence. In specific, the multifunctional CsPbI 3 QD film is fabricated through a simple yet efficient solid‐state‐ligand exchange process using a tailored organic ligand triphenyl phosphite (TPPI). The function of QD surface manipulation using TPPI here is proven to be twofold, balancing the carrier transport and effectively passivating the QD surface to produce conductive and emissive QD film. The CsPbI 3 perovskite QD solar cell delivers a ch ion efficiency of 15.21% with improved open circuit voltage and high fill factor. Concurrently functioning as a red LED, the CsPbI 3 perovskite QD solar cell outputs electric power to light conversion efficiency approaching 4%, a record value for QD electroluminescent PVs. The results here indicate that these versatile perovskite QDs may be a promising candidate for fabricating multifunctional optoelectronic devices.
Publisher: American Chemical Society (ACS)
Date: 12-2020
Publisher: Elsevier BV
Date: 03-2020
Publisher: American Physical Society (APS)
Date: 13-05-2004
Publisher: Elsevier BV
Date: 08-1970
Publisher: American Physical Society (APS)
Date: 07-01-2015
Publisher: Wiley
Date: 03-07-2021
Abstract: Critical catalysis studies often lack elucidation of the mechanistic role of defect equilibria in solid solubility and charge compensation. This approach is applied to interpret the physicochemical properties and catalytic performance of a free‐standing 2D–3D CeO 2− x scaffold, which is comprised of holey 2D nanosheets, and its heterojunctions with MoO 3− x and RuO 2 . The band gap alignment and structural defects are engineered using density functional theory (DFT) simulations and atomic characterization. Further, the heterojunctions are used in hydrogen evolution reaction (HER) and catalytic ozonation applications, and the impacts of the metal oxide heteroatoms are analyzed. A key outcome is that the principal regulator of the ozonation performance is not oxygen vacancies but the concentration of Ce 3+ and Ce vacancies. Cation vacancy defects are measured to be as high as 8.1 at% for Ru‐CeO 2− x . The homogeneous distribution of chemisorbed, Mo‐oxide, heterojunction nanoparticles on the CeO 2− x holey nanosheets facilitates intervalence charge transfer, resulting in the dominant effect and resultant ≈50% decrease in overpotential for HER. The heterojunctions are tested for aqueous‐catalytic ozonation of salicylic acid, revealing excellent catalytic performance from Mo doping despite the adverse impact of Ce vacancies. The present study highlights the use of defect engineering to leverage experimental and DFT results for band alignment.
Publisher: American Chemical Society (ACS)
Date: 12-03-2020
Publisher: American Chemical Society (ACS)
Date: 08-06-2023
Publisher: American Chemical Society (ACS)
Date: 24-02-2017
Abstract: In this study, we report the effect of doping in morphotropic BiFeO
Publisher: AIP Publishing
Date: 08-07-2011
DOI: 10.1063/1.3605601
Abstract: Molecular dynamics simulation is used to study the time-scales involved in the homogeneous melting of a superheated crystal. The interaction model used is an embedded-atom model for Fe developed in previous work, and the melting process is simulated in the microcanonical (N, V, E) ensemble. We study periodically repeated systems containing from 96 to 7776 atoms, and the initial system is always the perfect crystal without free surfaces or other defects. For each chosen total energy E and number of atoms N, we perform several hundred statistically independent simulations, with each simulation lasting for between 500 ps and 10 ns, in order to gather statistics for the waiting time τw before melting occurs. We find that the probability distribution of τw is roughly exponential, and that the mean value 〈τw〉 depends strongly on the excess of the initial steady temperature of the crystal above the superheating limit identified by other researchers. The mean 〈τw〉 also depends strongly on system size in a way that we have quantified. For very small systems of ∼100 atoms, we observe a persistent alternation between the solid and liquid states, and we explain why this happens. Our results allow us to draw conclusions about the reliability of the recently proposed Z method for determining the melting properties of simulated materials and to suggest ways of correcting for the errors of the method.
Publisher: Springer Science and Business Media LLC
Date: 17-10-2017
DOI: 10.1038/S41467-017-01081-7
Abstract: Solid-state cooling is an energy-efficient and scalable refrigeration technology that exploits the adiabatic variation of a crystalline order parameter under an external field (electric, magnetic, or mechanic). The mechanocaloric effect bears one of the greatest cooling potentials in terms of energy efficiency owing to its large available latent heat. Here we show that giant mechanocaloric effects occur in thin films of well-known families of fast-ion conductors, namely Li-rich (Li 3 OCl) and type-I (AgI), an abundant class of materials that routinely are employed in electrochemistry cells. Our simulations reveal that at room temperature AgI undergoes an adiabatic temperature shift of 38 K under a biaxial stress of 1 GPa. Likewise, Li 3 OCl displays a cooling capacity of 9 K under similar mechanical conditions although at a considerably higher temperature. We also show that ionic vacancies have a detrimental effect on the cooling performance of superionic thin films. Our findings should motivate experimental mechanocaloric searches in a wide variety of already known superionic materials.
Publisher: American Physical Society (APS)
Date: 16-03-2010
Publisher: Elsevier BV
Date: 09-2019
Publisher: American Chemical Society (ACS)
Date: 08-05-2020
DOI: 10.26434/CHEMRXIV.12268991.V1
Abstract: Functional oxide perovskites are the pillar of cutting-edge technological applications. Density functional theory (DFT) simulations are the theoretical methods of choice to understand and design perovskite materials. However, tests on the reliability of DFT to describe fundamental properties of oxide perovskites are scarce and mostly ill-defined due to a lack of rigorous theoretical benchmarks for solids. Here, we present a quantum Monte Carlo benchmark study of DFT on the archetypal perovskite BaTiO3 (BTO). It shows that no DFT approximation can simultaneously reproduce the energy, structure, and electronic density of BTO. Traditional protocols to select DFT approximations are empirical and fail to detect this shortcoming. An approach combining two different non-empirical DFT schemes, "SCAN" [1] and "HSE06" [2], is able to holistically describe BTO with accuracy. Combined DFT approaches should thus be considered as a promising alternative to standard methods for simulating oxide perovskites.
Publisher: American Physical Society (APS)
Date: 23-07-2008
Publisher: American Physical Society (APS)
Date: 30-09-2005
Publisher: Royal Society of Chemistry (RSC)
Date: 2020
DOI: 10.1039/C9SE00861F
Abstract: An air breathing planar PEMFC has thin geometry, open cathode and minimum peripheral devices.
Publisher: American Chemical Society (ACS)
Date: 02-06-2022
Publisher: Springer Science and Business Media LLC
Date: 03-06-2023
DOI: 10.1038/S41524-023-01057-W
Abstract: Perovskite oxides offer tremendous potential for applications in information storage and energy conversion, owing to a subtle interplay between their spin, charge, orbital and lattice degrees of freedom. Here, we further expand the possible range of perovskite oxides operation towards the fields of thermal management and thermal computing by exploiting an exceptional synergy between different ferroic orders. We propose dynamical control of the heat flow in a distinctive family of perovskite oxides obtained via the application of small electric (~10 kV/cm) and/or magnetic (~1 T) fields. Based on first-principles simulations, we predict a relative heat conductivity variation of ~100% in SrMnO 3 thin films near room temperature resulting from a phase transition that involves huge changes in both the magnetization and electric polarization. The disclosed giant multiphononic effects are fundamentally caused by anharmonic spin-phonon couplings that strongly influence the mean lifetime of phonons.
Publisher: American Chemical Society (ACS)
Date: 08-12-2022
Publisher: Springer Science and Business Media LLC
Date: 07-2016
DOI: 10.1038/SREP28742
Abstract: Coupling of order parameters provides a means to tune functionality in advanced materials including multiferroics, superconductors and ionic conductors. We demonstrate that the response of a frustrated ferroelectric state leads to coupling between order parameters under electric field depending on grain orientation. The strain of grains oriented along a specific crystallographic direction, 〈h00〉, is caused by converse piezoelectricity originating from a ferrodistortive tetragonal phase. For 〈hhh〉 oriented grains, the strain results from converse piezoelectricity and rotostriction, as indicated by an antiferrodistortive instability that promotes octahedral tilting in a rhombohedral phase. Both strain mechanisms combined lead to a colossal local strain of (2.4 ± 0.1) % and indicate coupling between oxygen octahedral tilting and polarization, here termed “rotopolarization”. These findings were confirmed with electromechanical experiments, in situ neutron diffraction and in situ transmission electron microscopy in 0.75Bi 1/2 Na 1/2 TiO 3 -0.25SrTiO 3 . This work demonstrates that polar and non-polar instabilities can cooperate to provide colossal functional responses.
Publisher: Wiley
Date: 29-11-2022
Abstract: Structural defects are ubiquitous for polycrystalline perovskite films, compromising device performance and stability. Herein, a universal method is developed to overcome this issue by incorporating halide perovskite quantum dots (QDs) into perovskite polycrystalline films. CsPbBr 3 QDs are deposited on four types of halide perovskite films (CsPbBr 3 , CsPbIBr 2 , CsPbBrI 2 , and MAPbI 3 ) and the interactions are triggered by annealing. The ions in the CsPbBr 3 QDs are released into the thin films to passivate defects, and concurrently the hydrophobic ligands of QDs self‐assemble on the film surfaces and grain boundaries to reduce the defect density and enhance the film stability. For all QD‐treated films, PL emission intensity and carrier lifetime are significantly improved, and surface morphology and composition uniformity are also optimized. Furthermore, after the QD treatment, light‐induced phase segregation and degradation in mixed‐halide perovskite films are suppressed, and the efficiency of mixed‐halide CsPbIBr 2 solar cells is remarkably improved to over 11% from 8.7%. Overall, this work provides a general approach to achieving high‐quality halide perovskite films with suppressed phase segregation, reduced defects, and enhanced stability for optoelectronic applications.
Publisher: Wiley
Date: 16-10-2021
Location: United Kingdom of Great Britain and Northern Ireland
Start Date: 02-2023
End Date: 02-2026
Amount: $516,000.00
Funder: Australian Research Council
View Funded ActivityStart Date: 02-2015
End Date: 01-2019
Amount: $621,374.00
Funder: Australian Research Council
View Funded Activity