Author
José A. Flores-Livas
Other affiliations: University of Basel, Claude Bernard University Lyon 1, Centre national de la recherche scientifique ...read more
Bio: José A. Flores-Livas is an academic researcher from Sapienza University of Rome. The author has contributed to research in topics: Superconductivity & Dopant. The author has an hindex of 20, co-authored 50 publications receiving 2527 citations. Previous affiliations of José A. Flores-Livas include University of Basel & Claude Bernard University Lyon 1.
Papers
More filters
••
Ghent University1, Forschungszentrum Jülich2, Åbo Akademi University3, Aalto University4, Vienna University of Technology5, Duke University6, University of Grenoble7, École Polytechnique Fédérale de Lausanne8, Durham University9, International School for Advanced Studies10, Max Planck Society11, Uppsala University12, Humboldt University of Berlin13, Fritz Haber Institute of the Max Planck Society14, Technical University of Denmark15, National Institute of Standards and Technology16, University of Udine17, Université catholique de Louvain18, University of Basel19, Harvard University20, University of California, Davis21, Rutgers University22, University of York23, Wake Forest University24, Science and Technology Facilities Council25, University of Oxford26, University of Vienna27, Dresden University of Technology28, Leibniz Institute for Neurobiology29, Radboud University Nijmegen30, University of Tokyo31, Centre national de la recherche scientifique32, University of Cambridge33, Royal Holloway, University of London34, University of California, Santa Barbara35, University of Luxembourg36, Los Alamos National Laboratory37, Harbin Institute of Technology38
TL;DR: A procedure to assess the precision of DFT methods was devised and used to demonstrate reproducibility among many of the most widely used DFT codes, demonstrating that the precisionof DFT implementations can be determined, even in the absence of one absolute reference code.
Abstract: The widespread popularity of density functional theory has given rise to an extensive range of dedicated codes for predicting molecular and crystalline properties. However, each code implements the formalism in a different way, raising questions about the reproducibility of such predictions. We report the results of a community-wide effort that compared 15 solid-state codes, using 40 different potentials or basis set types, to assess the quality of the Perdew-Burke-Ernzerhof equations of state for 71 elemental crystals. We conclude that predictions from recent codes and pseudopotentials agree very well, with pairwise differences that are comparable to those between different high-precision experiments. Older methods, however, have less precise agreement. Our benchmark provides a framework for users and developers to document the precision of new applications and methodological improvements.
1,141 citations
••
TL;DR: In this article, an allotrope of carbon with Cmmm symmetry was found to be more stable than graphite for pressures above 10 GPa, which is known as $Z$-carbon and is formed by pure $s{p}^{3}$ bonds.
Abstract: Through a systematic structural search we found an allotrope of carbon with Cmmm symmetry which we predict to be more stable than graphite for pressures above 10 GPa. This material, which we refer to as $Z$-carbon, is formed by pure $s{p}^{3}$ bonds and it provides an explanation to several features in experimental x-ray diffraction and Raman spectra of graphite under pressure. The transition from graphite to $Z$-carbon can occur through simple sliding and buckling of graphene sheets. Our calculations predict that $Z$-carbon is a transparent wide band-gap semiconductor with a hardness comparable to diamond.
275 citations
••
TL;DR: In this paper, the authors provide an up-to-date compendium of the available results on superconducting hydrides and explain how the synergy of different methodologies led to extraordinary discoveries in the field.
265 citations
••
University of the Basque Country1, Spanish National Research Council2, Donostia International Physics Center3, Sapienza University of Rome4, Max Planck Society5, Tohoku University6, National Institute for Materials Science7, University of Paris8, University of Tokyo9, Istituto Italiano di Tecnologia10
TL;DR: Quantum atomic fluctuations have a crucial role in stabilizing the crystal structure of the high-pressure superconducting phase of lanthanum hydride and are crucial for the stabilization of solids with high electron–phonon coupling constants that could otherwise be destabilized by the large electron– phonon interaction, thus reducing the pressures required for their synthesis.
Abstract: The discovery of superconductivity at 200 kelvin in the hydrogen sulfide system at high pressures1 demonstrated the potential of hydrogen-rich materials as high-temperature superconductors. Recent theoretical predictions of rare-earth hydrides with hydrogen cages2,3 and the subsequent synthesis of LaH10 with a superconducting critical temperature (Tc) of 250 kelvin4,5 have placed these materials on the verge of achieving the long-standing goal of room-temperature superconductivity. Electrical and X-ray diffraction measurements have revealed a weakly pressure-dependent Tc for LaH10 between 137 and 218 gigapascals in a structure that has a face-centred cubic arrangement of lanthanum atoms5. Here we show that quantum atomic fluctuations stabilize a highly symmetrical [Formula: see text] crystal structure over this pressure range. The structure is consistent with experimental findings and has a very large electron-phonon coupling constant of 3.5. Although ab initio classical calculations predict that this [Formula: see text] structure undergoes distortion at pressures below 230 gigapascals2,3, yielding a complex energy landscape, the inclusion of quantum effects suggests that it is the true ground-state structure. The agreement between the calculated and experimental Tc values further indicates that this phase is responsible for the superconductivity observed at 250 kelvin. The relevance of quantum fluctuations calls into question many of the crystal structure predictions that have been made for hydrides within a classical approach and that currently guide the experimental quest for room-temperature superconductivity6-8. Furthermore, we find that quantum effects are crucial for the stabilization of solids with high electron-phonon coupling constants that could otherwise be destabilized by the large electron-phonon interaction9, thus reducing the pressures required for their synthesis.
217 citations
••
TL;DR: In this article, the phase diagram and superconducting properties of the H-S systems were investigated by means of minima hopping method for structure prediction and density functional theory for superconductors.
Abstract: Due to its low atomic mass, hydrogen is the most promising element to search for
high-temperature phononic superconductors. However, metallic phases of hydrogen are only
expected at extreme pressures (400 GPa or higher). The measurement of the record
superconducting critical temperature of 203 K in a hydrogen-sulfur compound at 160 GPa of
pressure [A.P. Drozdov, M.I. Eremets, I.A. Troyan, arXiv:1412.0460
[cond-mat.supr-con] (2014); A.P. Drozdov, M.I. Eremets, I.A. Troyan, V.
Ksenofontov, S.I. Shylin, Nature 525, 73 (2015)], shows that metallization of
hydrogen can be reached at significantly lower pressure by inserting it in the matrix of
other elements. In this work we investigate the phase diagram and the superconducting
properties of the H-S systems by means of minima hopping method for structure prediction
and density functional theory for superconductors. We also show that Se-H has a similar
phase diagram as its sulfur counterpart as well as high superconducting critical
temperature. We predict H3Se to exceed 120 K superconductivity at 100 GPa. We show
that both H3Se and
H3S, due to the
critical temperature and peculiar electronic structure, present rather unusual
superconducting properties.
161 citations
Cited by
More filters
••
[...]
TL;DR: There is, I think, something ethereal about i —the square root of minus one, which seems an odd beast at that time—an intruder hovering on the edge of reality.
Abstract: There is, I think, something ethereal about i —the square root of minus one. I remember first hearing about it at school. It seemed an odd beast at that time—an intruder hovering on the edge of reality.
Usually familiarity dulls this sense of the bizarre, but in the case of i it was the reverse: over the years the sense of its surreal nature intensified. It seemed that it was impossible to write mathematics that described the real world in …
33,785 citations
01 May 1993
TL;DR: Comparing the results to the fastest reported vectorized Cray Y-MP and C90 algorithm shows that the current generation of parallel machines is competitive with conventional vector supercomputers even for small problems.
Abstract: Three parallel algorithms for classical molecular dynamics are presented. The first assigns each processor a fixed subset of atoms; the second assigns each a fixed subset of inter-atomic forces to compute; the third assigns each a fixed spatial region. The algorithms are suitable for molecular dynamics models which can be difficult to parallelize efficiently—those with short-range forces where the neighbors of each atom change rapidly. They can be implemented on any distributed-memory parallel machine which allows for message-passing of data between independently executing processors. The algorithms are tested on a standard Lennard-Jones benchmark problem for system sizes ranging from 500 to 100,000,000 atoms on several parallel supercomputers--the nCUBE 2, Intel iPSC/860 and Paragon, and Cray T3D. Comparing the results to the fastest reported vectorized Cray Y-MP and C90 algorithm shows that the current generation of parallel machines is competitive with conventional vector supercomputers even for small problems. For large problems, the spatial algorithm achieves parallel efficiencies of 90% and a 1840-node Intel Paragon performs up to 165 faster than a single Cray C9O processor. Trade-offs between the three algorithms and guidelines for adapting them to more complex molecular dynamics simulations are also discussed.
29,323 citations
•
28,685 citations
••
University of Udine1, École Polytechnique Fédérale de Lausanne2, University of Lugano3, Leipzig University4, University of Paris5, University of North Texas6, Princeton University7, National Research Council8, International School for Advanced Studies9, Cornell University10, University of Lincoln11, University of Milan12, École Polytechnique13, International Centre for Theoretical Physics14, University of Paderborn15, University of Oxford16, Jožef Stefan Institute17, University of Padua18, Sapienza University of Rome19, Vietnam Academy of Science and Technology20, University of British Columbia21, Centre national de la recherche scientifique22, University of Lorraine23, École Normale Supérieure24, University of Zurich25, Université Paris-Saclay26, Wake Forest University27, Temple University28
TL;DR: Recent extensions and improvements are described, covering new methodologies and property calculators, improved parallelization, code modularization, and extended interoperability both within the distribution and with external software.
Abstract: Quantum ESPRESSO is an integrated suite of open-source computer codes for quantum simulations of materials using state-of-the-art electronic-structure techniques, based on density-functional theory, density-functional perturbation theory, and many-body perturbation theory, within the plane-wave pseudopotential and projector-augmented-wave approaches Quantum ESPRESSO owes its popularity to the wide variety of properties and processes it allows to simulate, to its performance on an increasingly broad array of hardware architectures, and to a community of researchers that rely on its capabilities as a core open-source development platform to implement their ideas In this paper we describe recent extensions and improvements, covering new methodologies and property calculators, improved parallelization, code modularization, and extended interoperability both within the distribution and with external software
3,638 citations
••
University of Udine1, École Polytechnique Fédérale de Lausanne2, University of Lugano3, Leipzig University4, University of Paris5, University of North Texas6, Princeton University7, National Research Council8, International School for Advanced Studies9, Cornell University10, University of Lincoln11, University of Milan12, École Polytechnique13, International Centre for Theoretical Physics14, University of Paderborn15, University of Oxford16, Jožef Stefan Institute17, University of Padua18, Sapienza University of Rome19, Vietnam Academy of Science and Technology20, University of British Columbia21, Centre national de la recherche scientifique22, University of Lorraine23, École Normale Supérieure24, University of Zurich25, Université Paris-Saclay26, Wake Forest University27, Temple University28
TL;DR: Quantum ESPRESSO as discussed by the authors is an integrated suite of open-source computer codes for quantum simulations of materials using state-of-the-art electronic-structure techniques, based on density functional theory, density functional perturbation theory, and many-body perturbations theory, within the plane-wave pseudo-potential and projector-augmented-wave approaches.
Abstract: Quantum ESPRESSO is an integrated suite of open-source computer codes for quantum simulations of materials using state-of-the art electronic-structure techniques, based on density-functional theory, density-functional perturbation theory, and many-body perturbation theory, within the plane-wave pseudo-potential and projector-augmented-wave approaches. Quantum ESPRESSO owes its popularity to the wide variety of properties and processes it allows to simulate, to its performance on an increasingly broad array of hardware architectures, and to a community of researchers that rely on its capabilities as a core open-source development platform to implement theirs ideas. In this paper we describe recent extensions and improvements, covering new methodologies and property calculators, improved parallelization, code modularization, and extended interoperability both within the distribution and with external software.
2,818 citations