A5009879226- Advanced Chemical Physics Studies
- Machine Learning in Materials Science
- Molecular Junctions and Nanostructures
- Inorganic Fluorides and Related Compounds
- Catalysis and Oxidation Reactions
- X-ray Diffraction in Crystallography
- Spectroscopy and Quantum Chemical Studies
- Organic Electronics and Photovoltaics
- Semiconductor materials and devices
- X-ray Spectroscopy and Fluorescence Analysis
- Catalytic Processes in Materials Science
- Fullerene Chemistry and Applications
- Advanced NMR Techniques and Applications
- Photochemistry and Electron Transfer Studies
- Enzyme-mediated dye degradation
- Advanced Photocatalysis Techniques
- Surface and Thin Film Phenomena
- Electromagnetic Scattering and Analysis
- Water Quality Monitoring and Analysis
- Ga2O3 and related materials
- Quantum and electron transport phenomena
- Electronic and Structural Properties of Oxides
- Ammonia Synthesis and Nitrogen Reduction
- Antenna Design and Optimization
- Biotin and Related Studies
Argonne National Laboratory
2015-2024
Imperial College London
2011-2024
University of Bristol
2022-2024
Université Grenoble Alpes
2013-2023
UiT The Arctic University of Norway
2023
RIKEN Center for Computational Science
2023
The Abdus Salam International Centre for Theoretical Physics (ICTP)
2023
Thomas Young Centre
2016-2022
Universitat Politècnica de Catalunya
2021
Barcelona Supercomputing Center
2021
Electronic structure calculations have been instrumental in providing many important insights into a range of physical and chemical properties various molecular solid-state systems. Their importance to fields, including materials science, sciences, computational chemistry device physics, is underscored by the large fraction available public supercomputing resources devoted these calculations. As we enter exascale era, exciting new opportunities increase simulation numbers, sizes, accuracies...
We demonstrate that Daubechies wavelets can be used to construct a minimal set of optimized localized adaptively contracted basis functions in which the Kohn-Sham orbitals represented with an arbitrarily high, controllable precision. Ground state energies and forces acting on ions calculated this same accuracy as if they were directly basis, provided amplitude these is sufficiently small surface localization region, guaranteed by optimization procedure described work. This approach reduces...
We present an overview of the onetep program for linear-scaling density functional theory (DFT) calculations with large basis set (plane-wave) accuracy on parallel computers. The DFT energy is computed from matrix, which constructed spatially localized orbitals we call Non-orthogonal Generalized Wannier Functions (NGWFs), expressed in terms periodic sinc (psinc) functions. During calculation, both matrix and NGWFs are optimized localization constraints. By taking advantage localization, able...
Density Functional Theory calculations traditionally suffer from an inherent cubic scaling with respect to the size of system, making big extremely expensive. This can be avoided by use so-called linear algorithms, which have been developed during last few decades. In this way it becomes possible perform ab-initio for several tens thousands atoms or even more within a reasonable time frame. However, though algorithms is physically well justified, their implementation often introduces some...
MADNESS (multiresolution adaptive numerical environment for scientific simulation) is a high-level software solving integral and differential equations in many dimensions that uses fast harmonic analysis methods with guaranteed precision are based on multiresolution separated representations. Underpinning the capabilities powerful petascale parallel programming aims to increase both programmer productivity code scalability. This paper describes features of briefly discusses some current...
The BigDFT project was started in 2005 with the aim of testing advantages using a Daubechies wavelet basis set for Kohn–Sham (KS) density functional theory (DFT) pseudopotentials. This led to creation code, which employs computational approach optimal features flexibility, performance, and precision results. In particular, employed formalism has enabled implementation an algorithm able tackle DFT calculations large systems, up many thousands atoms, effort that scales linearly number atoms....
During the past decades, quantum mechanical methods have undergone an amazing transition from pioneering investigations of experts into a wide range practical applications, made by vast community researchers. First principles calculations systems containing up to few hundred atoms become standard in many branches science. The sizes which can be simulated increased even further during recent years, and quantum‐mechanical thousands are nowadays possible. This opens new appealing possibilities,...
Abstract Ga 2 O 3 and its polymorphs are attracting increasing attention. The rich structural space of polymorphic oxide systems such as offers potential for electronic structure engineering, which is particular interest a range applications, power electronics. γ‐Ga presents challenge across synthesis, characterization, theory due to inherent disorder resulting complex structure–electronic‐structure relationship. Here, density functional used in combination with machine‐learning approach...
By combining experiment and theory, this study unveils a direct link between the electronic states in metal hydrides their enthalpy of formation, advancing our understanding potential applications energy materials, catalysis, gas storage.
A new method for calculating optical absorption spectra within linear-scaling density-functional theory (LS-DFT) is presented, incorporating a scheme optimizing set of localized orbitals to accurately represent unoccupied Kohn-Sham states. Three different schemes are compared and the most promising these, based on use projection operator, has been implemented in fully-functional LS-DFT code. The applied calculation metal-free phthalocyanine molecule conjugated polymer poly(para-phenylene)....
A fast and accurate scheme has been developed to evaluate two key molecular parameters (on-site energies transfer integrals) that govern charge transport in organic supramolecular architecture devices. The is based on a constrained density functional theory (CDFT) approach implemented the linear-scaling BigDFT code exploits wavelet basis set. method applied model disordered structures generated by force-field simulations. role of environment taken into account building large clusters around...
Abstract In the past decade, developments of computational technology around density functional theory (DFT) calculations have considerably increased system sizes which can be practically simulated. The advent robust high performance computing algorithms scale linearly with size has unlocked numerous opportunities for researchers. This fact enables physicists and chemists to investigate systems are comparable routinely considered by experimentalists, leading collaborations a wide range...
The thermochromic properties of vanadium dioxide (VO2) offer great advantages for energy-saving smart windows, memory devices, and transistors. However, the crystallization solution-based thin films at temperatures lower than 400°C remains a challenge. Photonic annealing has recently been exploited to crystallize metal oxides, with minimal thermal damage substrate reduced manufacturing time. Here, VO2 films, obtained via green sol-gel process, were crystallized by pulsed excimer laser...
We report a linear-scaling density functional theory (DFT) study of the structure, wall-polarization absolute band-alignment and optical absorption several, recently synthesized, open-ended imogolite (Imo) nanotubes (NTs), namely single-walled (SW) aluminosilicate (AlSi), SW aluminogermanate (AlGe), methylated (AlSi-Me), double-walled (DW) AlGe NTs. Simulations with three different semi-local dispersion-corrected DFT-functionals reveal that NT can be increased by nearly factor four going...
Linear-scaling density functional theory simulation of methylated imogolite nanotubes (NTs) elucidates the interplay between wall-polarization, bands separation, charge-transfer excitation, and tunable electrostatics inside outside NT-cavity. The results suggest that integration polarization-enhanced selective photocatalysis chemical separation into one overall dipole-free material should be possible. Strategies are proposed to increase NT polarization for maximally enhanced electron–hole...
With the development of low order scaling methods for performing Kohn–Sham density functional theory, it is now possible to perform fully quantum mechanical calculations systems containing tens thousands atoms. However, with an increase in size system treated comes complexity, making challenging analyze such large and determine cause emergent properties. To address this issue, paper, we present a systematic complexity reduction methodology which can break down into their constituent...
Performing high accuracy hybrid functional calculations for condensed matter systems containing a large number of atoms is at present computationally very demanding or even out reach if quality basis sets are used. We highly optimized multiple graphics processing unit implementation the exact exchange operator which allows one to perform fast density-functional theory (DFT) with systematic without additional approximations up thousand atoms. With this method DFT become accessible on...
X-ray characterization techniques are invaluable for probing material characteristics and properties, have been instrumental in discoveries across materials research. However, there is a current lack of understanding how X-ray-induced effects manifest small molecular crystals. This particular concern as new sources with ever-increasing brilliance developed. In this paper, systematic studies X-ray–matter interactions reported on two industrially important catalysts, [Ir(COD)Cl]2 [Rh(COD)Cl]2,...
We present, within Kohn-Sham density functional theory calculations, a quantitative method to identify and assess the partitioning of large quantum-mechanical system into fragments. then show how this framework simple generalizations other well-known population analyses can be used extract, from first-principles, reliable electrostatic multipoles for identified Our approach reduces arbitrariness in fragmentation procedure enables possibility quantitatively whether corresponding fragment...
Abstract Amino acids are essential to all life. However, our understanding of some aspects their intrinsic structure, molecular chemistry, and electronic structure is still limited. In particular the nature amino in crystalline form, often biological medical processes, faces a lack knowledge both from experimental theoretical approaches. An important technique that has provided multitude crucial insights into chemistry materials x-ray photoelectron spectroscopy. While interpretation spectra...
Tungsten is an important and versatile transition metal has a firm place at the heart of many technologies. A popular experimental technique for characterisation tungsten tungsten-based compounds X-ray photoelectron spectroscopy (XPS), which enables assessment chemical states electronic structure through collection core level valence band spectra. However, in case metallic tungsten, open questions remain regarding origin, nature, position satellite features that are prominent spectrum. These...
Zirconia (zirconium dioxide) and hafnia (hafnium are binary oxides used in a range of applications. Because zirconium hafnium chemically equivalent, they have three similar polymorphs, it is important to understand the properties energetics these polymorphs. However, while density functional theory calculations can get correct energetic ordering, energy differences between polymorphs depend very much on specific approach, as do other quantities such lattice constants bulk modulus. We highly...
A recently developed linear-scaling density-functional theory (LS-DFT) formalism is used to calculate optical absorption spectra of hybrids C60 and the conjugated polymers poly(para-phenylene) (PPP) poly(para-phenylene vinylene) (PPV). The use a LS allows calculations on large systems with realistic proportions C60, which has been interest for such materials in photovoltaics. Two different bonding structures are tested hybrid PPP both additional peaks present below original onset absorption....
In a recent paper we presented linear scaling Kohn-Sham density functional theory (DFT) code based on Daubechies wavelets, where minimal set of localized support functions is optimized in situ and therefore adapted to the chemical properties molecular system. Thanks systematically controllable accuracy underlying basis set, this approach able provide an optimal contracted for given system: accuracies ground state energies atomic forces are same quality as uncontracted, cubic approach. This...