A5008894911- Thermal properties of materials
- High-pressure geophysics and materials
- Thermal Radiation and Cooling Technologies
- Advanced Thermoelectric Materials and Devices
- Geological and Geochemical Analysis
- Thermal Expansion and Ionic Conductivity
- Chalcogenide Semiconductor Thin Films
- Crystal Structures and Properties
- Advanced Chemical Physics Studies
- Graphene research and applications
- Phase-change materials and chalcogenides
- Topological Materials and Phenomena
- earthquake and tectonic studies
- X-ray Diffraction in Crystallography
- Semiconductor materials and devices
- Boron and Carbon Nanomaterials Research
- Quantum, superfluid, helium dynamics
- Physics of Superconductivity and Magnetism
- X-ray Spectroscopy and Fluorescence Analysis
- Clay minerals and soil interactions
- Advanced ceramic materials synthesis
- Ammonia Synthesis and Nitrogen Reduction
- Machine Learning in Materials Science
- Spectroscopy and Quantum Chemical Studies
- Quantum and electron transport phenomena
Institut de minéralogie, de physique des matériaux et de cosmochimie
2015-2024
Centre National de la Recherche Scientifique
2015-2024
Sorbonne Université
2015-2024
Institut de Recherche pour le Développement
2015-2024
Université Paris Cité
2014-2019
Délégation Ile-de-France Villejuif
2017
UPMC Health System
2017
Institute for Magnetospheric Physics
2017
Muséum national d'Histoire naturelle
2015
Scuola Internazionale Superiore di Studi Avanzati
2009-2012
QUANTUM ESPRESSO is an integrated suite of computer codes for electronic-structure calculations and materials modeling, based on density-functional theory, plane waves, pseudopotentials (norm-conserving, ultrasoft, projector-augmented wave). The acronym stands opEn Source Package Research in Electronic Structure, Simulation, Optimization. It freely available to researchers around the world under terms GNU General Public License. builds upon newly-restructured that have been developed tested...
Quantum ESPRESSO is an integrated suite of open-source computer codes for quantum simulations materials using state-of-the art electronic-structure techniques, based on density-functional theory, perturbation and many-body within the plane-wave pseudo-potential projector-augmented-wave approaches. owes its popularity to wide variety properties processes it allows simulate, performance increasingly broad array hardware architectures, a community researchers that rely capabilities as core...
A comparison of DFT methods Density functional theory (DFT) is now routinely used for simulating material properties. Many software packages are available, which makes it challenging to know the best use a specific calculation. Lejaeghere et al. compared calculated values equation states 71 elemental crystals from 15 different widely codes employing 40 potentials (see Perspective by Skylaris). Although there were variations in values, most recent and converged toward single value, with...
We characterize the thermal conductivity of graphite, monolayer graphene, graphane, fluorographane, and bilayer solving exactly Boltzmann transport equation for phonons, with phonon–phonon collision rates obtained from density functional perturbation theory. For results are found to be in excellent agreement experiments; notably, is 1 order magnitude larger than what by single mode approximation, commonly used describe heat transport. we point out that a meaningful value intrinsic at room...
The conduction of heat in two dimensions displays a wealth fascinating phenomena key relevance to the scientific understanding and technological applications graphene related materials. Here, we use density-functional perturbation theory an exact, variational solution Boltzmann transport equation study fully from first-principles phonon conductivity graphene, boron nitride, molybdenum disulphide functionalized derivatives graphane fluorographene. In all these materials, at variance with...
Abstract W annier90 is an open-source computer program for calculating maximally-localised Wannier functions (MLWFs) from a set of Bloch states. It interfaced to many widely used electronic-structure codes thanks its independence the basis sets representing these In past few years development has transitioned community-driven model; this resulted in number new developments that have been recently released v3.0. article we describe functionalities, include implementation features...
We present a first-principles theoretical approach for evaluating the lattice thermal conductivity based on exact solution of Boltzmann transport equation. use variational principle and conjugate gradient scheme, which provide us with an algorithm faster than one previously used in literature able to always converge [Omini Sparavigna, Physica B: Condens. Matter 212, 101 (1995)]. Three-phonon normal umklapp collisions, isotope scattering, border effects are rigorously treated calculation....
We have implemented a generic method, based on the $2n+1$ theorem within density functional perturbation theory, to calculate anharmonic scattering coefficients among three phonons with arbitrary wave vectors. The method is used study phonon broadening in graphite and graphene mono- bilayers. of high-energy optical branches highly nonuniform presents series sudden steps spikes. At finite temperature, two linearly dispersive acoustic TA LA nonzero for small bilayer is, overall, very similar...
The self-consistent harmonic approximation is an effective theory to calculate the free energy of systems with strongly anharmonic atomic vibrations, and its stochastic implementation has proved be efficient method study, from first-principles, properties solids. as a function average positions (centroids) can used study quantum or thermal lattice instability. In particular centroids are order parameters in second-order structural phase transitions such as, e.g., charge-density-waves...
Since 2014 the layered semiconductor SnSe in high-temperature Cmcm phase is known to be most efficient intrinsic thermoelectric material. Making use of first-principles calculations we show that its vibrational and thermal transport properties are determined by huge nonperturbative anharmonic effects. We transition from low-symmetry Pnma a second-order driven collapse zone border phonon, whose frequency vanishes at temperature. Our spectral function in-plane modes strongly anomalous with...
Thermal transport is a key feature for the operation of phase change memory devices which rest on fast and reversible transformation between crystalline amorphous phases chalcogenide alloys upon Joule heating. In this paper we report ab initio calculations bulk thermal conductivity prototypical compounds ${\mathrm{Ge}}_{2}{\mathrm{Sb}}_{2}{\mathrm{Te}}_{5}$ GeTe in their form. The related ${\mathrm{Sb}}_{2}{\mathrm{Te}}_{3}$ compound also investigated sake comparison. obtained from solution...
The variational stochastic self-consistent harmonic approximation is combined with the calculation of third-order anharmonic coefficients within density functional perturbation theory and $2n+1$ theorem to calculate properties crystals. It demonstrated that in perturbative limit, combination these two methods yields phonon linewidth frequency shift a very efficient way, avoiding explicit fourth-order coefficients. Moreover, it also allows calculating lifetimes inelastic neutron-scattering...
At room temperature, PbTe and SnTe are efficient thermoelectrics with a cubic structure. low undergoes ferroelectric transition critical temperature strongly dependent on the hole concentration, while is an incipient ferroelectric. By using stochastic self-consistent harmonic approximation, we investigate anharmonic phonon spectra occurrence of in both systems. We find that vibrational depend approximation used for exchange-correlation kernel density-functional theory. If gradient...
SnS and SnSe are isoelectronic materials with a common phase diagram. Recently, was found to be the most efficient intrinsic thermoelectric material in its high-temperature Cmcm above 800 K. Making use of first-principles calculations, here we show that electronic vibrational properties both very similar this and, consequently, is also expected have high figure merit at temperature phase. In fact, power factor lattice thermal conductivity comparable for materials, which ensures merit. As...
We report a density-functional theory (DFT)-based study of the interface bulk water with prototypical oxide surface, MgO(001), and focus our on often-overlooked surface electric field.
Pressure-induced phase transitions in GeTe, a prototype change material, have been studied to date with diffraction which is not sensitive anharmonicity-induced dynamical effects. GeTe also prone surface oxidation may compromise measurements. These factors could be responsible for the lack of clarity about phases and intervening diagram GeTe. We used high-pressure Raman scattering ab initio pseudopotential density functional calculations unambiguously establish identify three up 57 GPa,...
Pressure- and temperature-dependent Raman scattering in GeSe, SnSe, GeTe for pressures beyond 50 GPa temperatures ranging from 78 to 800 K allow us identify structural electronic phase transitions, similarities between GeSe differences with GeTe. Calculations help deduce the propensity of defect formation doping that results it, which gives rise strong damping anomalous anharmonicity. These properties are related underlying chemical bonding consistent a recent classification several...
Advanced semiempirical calculations have been performed to compute simultaneously optical absorption and $K$ pre-edge x-ray spectra of ${\mathrm{Fe}}^{2+}$ in four distinct site symmetries found minerals. The symmetries, i.e., a distorted octahedron, tetrahedron, square planar site, trigonal bipyramidal are representative the sites crystals glasses. A particular attention has paid definition $p\text{\ensuremath{-}}d$ hybridization Hamiltonian which occurs for noncentrosymmetric order account...
Bismuth is one of the rare materials in which second sound has been experimentally observed. Our exact calculations thermal transport with Boltzmann equation predict occurrence this Poiseuille phonon flow between $\ensuremath{\approx}1.5$ and $\ensuremath{\approx}3.5\text{ }\text{ }\mathrm{K}$, a sample size 3.86 9.06 mm, consistent experimental observations. Hydrodynamic heat characteristics are given for any temperature: wave propagation length, drift velocity, Knudsen number. We discuss...
Among the inorganic compounds, many oxides and sulfides are known to be semiconductors. At crossroads of these two families, oxysulfide MxOySz compounds were much less investigated because they scarce in nature complex synthesize. them, lanthanide Ln2O2S (Ln = lanthanide) indirect band gap semiconductors, with wide gaps, except for Ce2O2S. (Gd,Ce)2O2S anisotropic nanoparticles a hexagonal structure obtained over whole composition range exhibit colors varying from white brown increasing Ce...
The mechanism of photomagnetism in copper octacyanomolybdate molecules is currently under debate. Contrary to the general belief that photomagnetic transition occurs only due a photoinduced electron transfer from molybdenum atom, recent X-ray magnetic dichroic (XMCD) data clearly indicate this phenomenon associated at low temperature local low-spin-high-spin on atom. In article we provide theoretical justification for these experimental facts. We show first simulation absorption (XAS) and...
A combined experimental-theoretical study on the temperature dependence of X-ray absorption near-edge structure (XANES) and nuclear magnetic resonance (NMR) spectra periclase (MgO), spinel (MgAl2O4), corundum (α-Al2O3), berlinite (α-AlPO4), stishovite α-quartz (SiO2) is reported. Predictive calculations are presented when experimental data not available. For these light-element oxides, both techniques detect systematic effects related to quantum thermal vibrations which well reproduced by...
Hand-on routes to reduce lattice thermal conductivity (LTC) in bismuth have been explored by employing a combination of Boltzmann's transport equation and ab initio calculations phonon-phonon interaction within the density functional perturbation theory. We first obtained temperature dependence bulk LTC excellent agreement with available experiments. A very accurate microscopic description heat has achieved electronic contribution determined. By controlling interplay between phonon...
An efficient first-principles approach to calculate x-ray magnetic circular dichroism (XMCD) and natural (XNCD) is developed applied in the near-edge region at $K$ ${L}_{1}$ edges solids. Computation of requires precise calculations absorption spectra (XAS) for circularly polarized light. For derivation XAS cross section, we used a relativistic description photon-electron interaction that results an additional term section couples electric dipole operator with...