Roadmap on Electronic Structure Codes in the Exascale Era

Electronic structure calculations have been instrumental in providing many important insights into a range of physical and chemical properties of various molecular and solid-state systems. Their importance to various fields, including materials science, chemical sciences, computational chemistry and device physics, is underscored by the large fraction of available public supercomputing resources devoted to these calculations. As we enter the exascale era, exciting new opportunities to increase simulation numbers, sizes, and accuracies present themselves. In order to realize these promises, the community of electronic structure software developers will however first have to tackle a number of challenges pertaining to the efficient use of new architectures that will rely heavily on massive parallelism and hardware accelerators. This roadmap provides a broad overview of the state-of-the-art in electronic structure calculations and of the various new directions being pursued by the community. It covers 14 electronic structure codes, presenting their current status, their development priorities over the next five years, and their plans towards tackling the challenges and leveraging the opportunities presented by the advent of exascale computing

Roadmap on Electronic Structure Codes in the Exascale Era

Electronic structure calculations have been instrumental in providing many important insights into a range of physical and chemical properties of various molecular and solid-state systems. Their importance to various fields, including materials science, chemical sciences, computational chemistry and device physics, is underscored by the large fraction of available public supercomputing resources devoted to these calculations. As we enter the exascale era, exciting new opportunities to increase simulation numbers, sizes, and accuracies present themselves. In order to realize these promises, the community of electronic structure software developers will however first have to tackle a number of challenges pertaining to the efficient use of new architectures that will rely heavily on massive parallelism and hardware accelerators. This roadmap provides a broad overview of the state-of-the-art in electronic structure calculations and of the various new directions being pursued by the community. It covers 14 electronic structure codes, presenting their current status, their development priorities over the next five years, and their plans towards tackling the challenges and leveraging the opportunities presented by the advent of exascale computing

Roadmap on Electronic Structure Codes in the Exascale Era

Electronic structure calculations have been instrumental in providing many important insights into a range of physical and chemical properties of various molecular and solid-state systems. Their importance to various fields, including materials science, chemical sciences, computational chemistry and device physics, is underscored by the large fraction of available public supercomputing resources devoted to these calculations. As we enter the exascale era, exciting new opportunities to increase simulation numbers, sizes, and accuracies present themselves. In order to realize these promises, the community of electronic structure software developers will however first have to tackle a number of challenges pertaining to the efficient use of new architectures that will rely heavily on massive parallelism and hardware accelerators. This roadmap provides a broad overview of the state-of-the-art in electronic structure calculations and of the various new directions being pursued by the community. It covers 14 electronic structure codes, presenting their current status, their development priorities over the next five years, and their plans towards tackling the challenges and leveraging the opportunities presented by the advent of exascale computing.Comment: Submitted as a roadmap article to Modelling and Simulation in Materials Science and Engineering; Address any correspondence to Vikram Gavini ([email protected]) and Danny Perez ([email protected]

DFT-NMR Investigation and V-51 3QMAS Experiments for Probing Surface OH Ligands and the Hydrogen-Bond Network in a Polyoxovanadate Cluster: The Case of Cs-4[H2V10O28]center dot 4H(2)O

International audienceThis work shows that the combination of first-principles calculations and V-51 NMR experiments is a powerful tool to elucidate the location of surface hydroxyl groups and to precisely describe the hydrogen bond network in the complex decavanadate cluster Cs-4[H2V10O28]center dot 4H(2)O, enhancing the strength of NMR crystallography. The detailed characterization of H-bond networks for these kinds of inorganic compounds is of primary importance and should benefit from the DFT-NMR predictions by considering explicitly the periodic boundary conditions. The determination of the CS4[H2V10O28]center dot 4H(2)O structure by single-crystal X-ray diffraction was not sufficiently accurate to provide the location of protons. From available diffraction data, five different protonated model structures have been built and optimized using DFT-based methods. The possible interconversion of two decavanadate isomers through a proton exchange is evaluated by calculating the energy barrier and recording variable-temperature H-1 MAS NMR spectra. First-principles calculations of V-51 NMR parameters clearly indicate that these parameters are very sensitive to the local intermolecular hydrogen-bonding interactions. Considering the OFT error limits, the fairly good agreement between calculated and experimental NMR parameters arising from the statistical modeling of the data allows the unambiguous assignment of the five V-51 NMR signals and, thus, the location of OH surface ligands in the decavanadate cluster. In particular, first-principles calculations accurately reproduce the V-51 quadrupolar parameters. These results are fully consistent with V-51 3QMAS NMR spectra recorded with and without H-1 decoupling. Finally, correlations are established between local octahedral VO6 deformations and V-51 NMR parameters (C-q and Delta delta), which will be useful for the characterization of a wide range of chemical species containing vanadium(V)

Studies of covalent amides for hydrogen storage systems: Structures and bonding of the MAl(NH2)4 phases with M = Li, Na and K

Mixtures of metallic amides and LiH are studied as hydrogen storage materials. We show that the amides decomposition temperature decreases as the polarizing effect of the metallic cation increases, hence our interest for amides with strong polarizing cations such as Al3+. Studying the MAl(NH2)4 phases with M = Li, Na and K, we tried to rationalize such metal-decomposition temperature dependence and found from IR spectroscopy investigations supported by DFT calculations that smaller is the alkali cation M+, more the Al(NH2)4 and M(NH2)4 tetrahedra are interconnected in the crystal structures and higher is the decomposition temperature. Regarding applications, the possibility of using the LiAl(NH2)4-LiH mixture as a reversible hydrogen storage material is discussed. If such mixture is able to release up to 6.2 mass% of hydrogen at 130 °C, it is shown that the LiAl(NH2)4 decomposition leads to the formation of amorphous LiAl(NH)2 imide, which is unfortunately metastable and exothermically transformed into LiNH2 + AlN. This last reaction is highly problematic for hydrogen storage applications as it is fully irreversible and AlN does not react with hydrogen under moderate temperature and pressure conditions. © 2010 Elsevier B.V. All rights reserved

Large scale and linear scaling DFT with the CONQUEST code

We survey the underlying theory behind the large-scale and linear scaling density functional theory code, conquest, which shows excellent parallel scaling and can be applied to thousands of atoms with diagonalization and millions of atoms with linear scaling. We give details of the representation of the density matrix and the approach to finding the electronic ground state and discuss the implementation of molecular dynamics with linear scaling. We give an overview of the performance of the code, focusing in particular on the parallel scaling, and provide examples of recent developments and applications.Web of Science5216art. no. 16411