A5031544598- High-pressure geophysics and materials
- Nuclear Materials and Properties
- Electronic and Structural Properties of Oxides
- Rare-earth and actinide compounds
- Advanced Chemical Physics Studies
- Magnetic and transport properties of perovskites and related materials
- Advancements in Solid Oxide Fuel Cells
- Boron and Carbon Nanomaterials Research
- Semiconductor materials and devices
- Machine Learning in Materials Science
- Chemical Looping and Thermochemical Processes
- Fuel Cells and Related Materials
- Radioactive element chemistry and processing
- Diamond and Carbon-based Materials Research
- Advanced Condensed Matter Physics
- nanoparticles nucleation surface interactions
- Microstructure and mechanical properties
- High-Velocity Impact and Material Behavior
- Quantum, superfluid, helium dynamics
- Catalytic Processes in Materials Science
- Crystallography and molecular interactions
- Thermodynamic and Structural Properties of Metals and Alloys
- Laser-induced spectroscopy and plasma
- Thermal Expansion and Ionic Conductivity
- Muon and positron interactions and applications
Commissariat à l'Énergie Atomique et aux Énergies Alternatives
2015-2024
CEA DAM Île-de-France
2015-2024
Université Paris-Saclay
2020-2024
CEA Paris-Saclay
2020-2024
Sorbonne Université
2003-2007
Centre National de la Recherche Scientifique
2003-2007
Université Paris Cité
2003-2007
Institut des NanoSciences de Paris
2004-2007
Center for MathematicaL studies and their Applications
2007
École Normale Supérieure Paris-Saclay
2007
abinit is probably the first electronic-structure package to have been released under an open-source license about 20 years ago. It implements density functional theory, density-functional perturbation theory (DFPT), many-body (GW approximation and Bethe–Salpeter equation), more specific or advanced formalisms, such as dynamical mean-field (DMFT) “temperature-dependent effective potential” approach for anharmonic effects. Relying on planewaves representation of wavefunctions, density, other...
We report ab initio calculations of the structural, electronic, optical, and thermodynamic properties plutonium oxides (${\text{PuO}}_{2}$ $\ensuremath{\beta}{\text{-Pu}}_{2}{\text{O}}_{3}$). In order to describe basic features electronic structure, a method suited take into account strong local correlations has be used. apply density approximation/generalized gradient approximation ($\text{LDA}/\text{GGA})+U$ approximations these compounds compare them with Sun et al. [J. Chem. Phys. 128,...
The electronic and atomic structures of several $(1\ifmmode\times\else\texttimes\fi{}1)$ terminations the (110) polar orientation ${\mathrm{SrTiO}}_{3}$ surface are systematically studied by first-principles calculations. structure two stoichiometric SrTiO ${\mathrm{O}}_{2}$ characterized marked differences with respect to bulk, as a consequence polarity compensation. In former, Fermi level is located at bottom conduction band, while in latter formation peroxo bond between oxygens results...
The melting curve of aluminum is determined up to 300 GPa using ab initio molecular dynamics simulations. calculations are based on density functional theory within the generalized gradient approximation. We simulate with two methods, one-phase or heat until it melts and two-phase approaches. first one corresponds a homogeneous melting, while second involves heterogeneous materials. This conceptual difference gives rise temperatures which can noticeably differ. As expected we observe...
The high pressure-temperature behavior of titanium has been studied with x-ray diffraction in resistively heated and laser-heated diamond anvil cells up to 200 GPa $\ensuremath{\sim}3500$ K. stability fields $\ensuremath{\alpha}\text{\ensuremath{-}}\mathrm{Ti},\ensuremath{\omega}\text{\ensuremath{-}}\mathrm{Ti},\ensuremath{\beta}\text{\ensuremath{-}}\mathrm{Ti},\ensuremath{\gamma}\text{\ensuremath{-}}\mathrm{Ti}$, $\ensuremath{\delta}\text{\ensuremath{-}}\mathrm{Ti}$ have determined this...
We present an ab initio study of MgO at high temperature and pressure, around the phase transition between B1 B2 phases. By means molecular dynamic calculations, thermal evolution vibrational properties thermodynamic quantities is obtained. carefully compare our results with previous theoretical works on curve we analyze differences among them. show that anharmonic effects have been underestimated in quasiharmonic approximation their inclusion free energy strongly straightens up curve. Then,...
Hydration and oxidation of gadolinium-doped barium cerate, a system with highly promising properties when used as electrolyte for protonic ceramic fuel cells, are investigated by means density functional calculations. The energy landscape oxygen vacancies interstitial protons in this strongly distorted orthorhombic perovskite is computed. Although the most stable sites found close vicinity dopant, picture very complex emerges, which some far away from Gd more than other ones its vicinity,...
Quantum nuclear zero-point motions in solid ${\mathrm{H}}_{2}$ and ${\mathrm{D}}_{2}$ under pressure are investigated at 80 K up to 160 GPa by first-principles path-integral molecular dynamics calculations. Molecular orientations well defined phase II of ${\mathrm{D}}_{2}$, while exhibits large very asymmetric angular quantum fluctuations this phase, with possible rotation the ($bc$) plane, making it difficult associate a well-identified single classical structure. The mechanism for...
The phase diagram of uranium has been explored up to 100 GPa and 2000 K by means ab initio molecular dynamics (AIMD) simulations. lattice energetics the stable phases observed experimentally in this range pressure temperature are studied work. phonon spectra $\ensuremath{\alpha}$ $\ensuremath{\gamma}$ shown evolve strongly as a function temperature, unveiling huge anharmonic effects present material. If elastics constants bulk shear moduli do not disclose any effects, modulus decreases...
We build an ``all-electron'' norm-conserving pseudopotential for boron which extends the use of ab initio molecular dynamics simulations up to 50 times normal density ${\ensuremath{\rho}}_{0}$. This allows us perform dense plasmas from regime where quantum mechanical effects are important semiclassical based on Thomas-Fermi approach are, by default, only simulation method currently available. study first one establish, case boron, is legitimate and sufficient. It further brings forward...
The diffusion barriers of protonic defects in Gd-doped BaCeO${}_{3}$, a compound candidate as electrolyte for ceramic fuel cells, have been investigated by density functional theory calculations, starting from previously computed energy landscape consisting 16 kinds stable sites (eight close to dopants and eight far them). simplified string method has used determine accurately the minimum paths between those that might imply either proton reorientations, intraoctahedral, or interoctahedral...
The high-pressure melting curve of titanium has been studied up to 120 GPa and $\ensuremath{\sim}3500$ K using both laser-heated diamond anvil cells ab initio molecular dynamic simulations. Several theoretical experimental diagnostics, including x-ray diffraction, are tested compared. Using the most accurate on sides, a fair agreement can be reached between experiments observation temperature plateaus, diagnostic proposed for cell experiments, is not reliable here. obtained here higher (by...
The formation enthalpy of a monovacancy in gold and aluminum under the condition intense laser irradiation is evaluated by means ab initio calculations. These simulations are performed using norm-conserving pseudopotentials taking advantage an efficient parallelization scheme. Using constant-pressure for set electronic temperatures ranging from $0.01\phantom{\rule{0.3em}{0ex}}\text{to}\phantom{\rule{0.3em}{0ex}}6.0\phantom{\rule{0.3em}{0ex}}\mathrm{eV}$, fully relaxed geometries thus...
In this article, we performed accurate ab initio calculations in order to address the influence of electronic correlations on surface stability PuO${}_{2}$. Various terminations (100), (110), and (111) orientations were considered, among which some are polar. Standard density-functional theory (DFT), is known provide a poor description structure plutonium oxides, predicts an unexpected stabilization polar uncompensated O${}_{2}$-(111) Pu-(111). We show that shortcoming no longer observed...
By means of ab initio molecular dynamics calculations, the thermal evolution vibrational properties in $\ensuremath{\alpha}$-U is studied at low temperature. The phase transition undergone by this material around 50 K was previously extensively using calculations framework linear response 0 K. Although these previous efforts capture successfully complexity experimental phonon spectrum room temperature, particular soft-phonon mode and its pressure dependence, they fail to reproduce...
Ab initio molecular dynamics calculations are used to investigate the vibrational properties of high-temperature $\ensuremath{\delta}$ and $\ensuremath{\epsilon}$ phases plutonium. We combine local-density approximation (LDA)$+U$ for strong electron correlations temperature-dependent effective potential method in order calculate phonon spectra two phases, as well their dependence on temperature. Our results show that phase can only be stabilized when temperature simultaneously accounted for....
The $\ensuremath{\gamma}\text{\ensuremath{-}}\mathrm{U}\ensuremath{-}\mathrm{Mo}$ alloys have been studied by means of ab initio molecular-dynamic simulations at 900 K as a function the Mo concentration (0%, 25%, 50%, 75%, and 100%). Using temperature-dependent effective potential method with symmetry-imposed force constant extension, we obtained vibrational, thermodynamic, elastic properties U--Mo, including anharmonicity disorder. We show that addition temperature effects are responsible...
X-ray diffraction measurements performed in a diamond anvil cell under quasihydrostatic conditions up to 142 GPa at 300 K evidence an $\ensuremath{\alpha}$-Zr $\ensuremath{\rightarrow}$ (17 GPa) $\ensuremath{\omega}$-Zr (35 $\ensuremath{\beta}$-Zr phase transitions sequence. Ab initio molecular dynamics calculations on the body-centered cubic and 1000 between 0 100 produced equation of state excellent agreement with experiments. The stability pressure has been verified by numerical...