Paul Loubeyre

Commissariat à l'Énergie Atomique et aux Énergies Alternatives

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Mohamed Mézouar

European Synchrotron Radiation Facility

J. H. Eggert

Lawrence Livermore National Laboratory

Agnès Dewaele

Commissariat à l'Énergie Atomique et aux Énergies Alternatives

Raymond Jeanloz

University of California, Berkeley

P. M. Celliers

Lawrence Livermore National Laboratory

F. Occelli

CEA DAM Île-de-France

S. Brygoo

CEA DAM Île-de-France

Gunnar Weck

CEA DAM Île-de-France

R. LeToullec

Sorbonne Université

D. G. Hicks

Swinburne University of Technology

Cooperative Institutions

Commissariat à l'Énergie Atomique et aux Énergies Alternatives

Centre National de la Recherche Scientifique

Lawrence Livermore National Laboratory

CEA DAM Île-de-France

Sorbonne Université

CEA Paris-Saclay

Université Paris-Saclay

École Polytechnique

University of Rochester

European Synchrotron Radiation Facility

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Brillouin scattering and three-body forces in argon at high pressures

Physical review. B, Condensed matter (1986)

M. Grimsditch Paul Loubeyre A. Polian

Brillouin scattering was measured at room temperature in liquid and solid argon in a diamond-anvil cell at pressures up to 33 GPa. In the fluid, our results agree well with those obtained by ultrasonic methods. In the solid, the elastic anisotropy and the use of the experimental equation of state allowed us to determine limiting values for all the elastic constants as a function of pressure. We also performed self-consistent phonon calculations using various pair potentials proposed for argon. From the comparison between calculation and experiment it can be stated that in dense solid argon there is no way to reproduce the experimental results with any pair potential and that many-body exchange potentials have to be incorporated for an accurate description.

Limiting

Brillouin zone

10.1103/physrevb.33.7192

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Citations (141)

Extended data set for the equation of state of warm dense hydrogen isotopes

Physical Review B (2012)

Paul Loubeyre S. Brygoo J. H. Eggert P. M. Celliers D. K. Spaulding

Laser-driven shock wave measurements on hydrogen and deuterium precompressed in diamond anvil cells from 0.16 to 1.6 GPa provide new shock Hugoniot data over a significantly broader range of density-temperature phase space than was previously achievable. Observations of shock velocity and thermal emission provide complete equation of state data (pressure, density, internal energy, and temperature) in the dense fluid regime up to 175 GPa. This data set is used to benchmark recent advanced ab initio calculations and is seen to be in good agreement with a maximum $8%$ density difference above 100 GPa. Thermodynamic quantities (specific heat and Gruneisen coefficient) are calculated directly from the data and compared to theory. Optical reflectivity data show a continuous transition from an electrically insulating to conducting fluid state and reveal that this transition is increasingly sensitive to temperature with increasing density. Ab initio calculations are observed to underestimate the temperature onset of metallization.

Diamond anvil cell

10.1103/physrevb.86.144115

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Citations (103)

Melting of lead under high pressure studied using second-scale time-resolved x-ray diffraction

Physical Review B (2007)

Agnès Dewaele Mohamed Mézouar Nicolas Guignot Paul Loubeyre

The high pressure and high temperature phase diagram of lead has been studied up to $80\phantom{\rule{0.3em}{0ex}}\mathrm{GPa}$ and $3700\phantom{\rule{0.3em}{0ex}}\mathrm{K}$ in a laser-heated diamond anvil cell. Melting and solid-solid phase transitions have been followed with a second scale by in situ synchrotron time-resolved x-ray diffraction. The detection of the x-ray signal scattered by the liquid was used as an objective criterion for melting. We evidenced that the melting phenomenon in a diamond anvil cell has a typical lifetime that can be as low as $1\phantom{\rule{0.3em}{0ex}}\mathrm{s}$. Unlike a previous laser-heated diamond anvil cell study, the measured melting curve is in agreement with melting points detected using dynamic compression and confirms the predictions of ab initio calculations. The pressure-temperature conditions of the hcp-bcc phase transition have been measured, and the hcp-bcc-liquid triple point has been located around $39\phantom{\rule{0.3em}{0ex}}\mathrm{GPa}$ and $2400\phantom{\rule{0.3em}{0ex}}\mathrm{K}$.

Diamond anvil cell

Triple point

Melting curve analysis

10.1103/physrevb.76.144106

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Citations (109)

The α → ω phase transformation in zirconium followed with ms-scale time-resolved X-ray absorption spectroscopy

High Pressure Research (2016)

Agnès Dewaele Rémi F. André F. Occelli Olivier Mathon S. Pascarelli

The conditions of the pressure-induced α→ω phase transformation in zirconium have been reported to be influenced by the sample purity, the pressurizing conditions, and the deformation rate. Here, we study this transformation using a dynamic diamond-anvil cell compression setup and ms-scale time-resolved X-ray absorption spectroscopy. The sample pressure is also monitored at the same timescale using the ruby luminescence method. For the samples used in this study (polycrystal of 99.9+ purity, hydrostatically compressed in neon pressure transmitting medium), the phase transformation pressure is very close in static (11 GPa) and in dynamic (12±1 GPa) compression and the transformation is achieved in less than a few ms at 12 GPa. Comparison with literature studies suggest that the kinetics and the mechanism of this martensitic phase transformation are different under hydrostatic and non-hydrostatic compression.

Diamond anvil cell

Hydrostatic pressure

Hydrostatic equilibrium

Diffusionless transformation

10.1080/08957959.2016.1199692

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Citations (14)

Toroidal diamond anvil cell for detailed measurements under extreme static pressures

Nature Communications (2018)

Agnès Dewaele Paul Loubeyre F. Occelli Olivier Marie Mohamed Mézouar

Over the past 60 years, the diamond anvil cell (DAC) has been developed into a widespread high static pressure device. The adaptation of laboratory and synchrotron analytical techniques to DAC enables a detailed exploration in the 100 GPa range. The strain of the anvils under high load explains the 400 GPa limit of the conventional DAC. Here we show a toroidal shape for a diamond anvil tip that enables to extend the DAC use toward the terapascal pressure range. The toroidal-DAC keeps the assets for a complete, reproducible, and accurate characterization of materials, from solids to gases. Raman signal from the diamond anvil or X-ray signal from the rhenium gasket allow measurement of pressure. Here, the equations of state of gold, aluminum, and argon are measured with X-ray diffraction. The data are compared with recent measurements under similar conditions by two other approaches, the double-stage DAC and the dynamic ramp compression.

Diamond anvil cell

Gasket

SIGNAL (programming language)

10.1038/s41467-018-05294-2

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Citations (146)

Single crystal x-ray diffraction with a synchrotron source in a mdac at low temperature

High Pressure Research (1992)

R. Le Toullec Paul Loubeyre J. P. Pinceaux H. K. Mao Jing Hu

Abstract A new diamond anvil cell and a helium flow cryostat have been developed for x-ray diffraction on single crystals at low temperatures and high pressures using the white radiation of a synchrotron beam. This novel instrument especially enables continuous change of sample temperature and pressure without any adjustment of alignment. A minimum temperature of 46 K has been reached. Presented at the IUCr Workshop on ‘Synchrotron Radiation Instrumentation for High Pressure Crystallography’, Daresbury Laboratory 20-21 July 1991

Cryostat

Diamond anvil cell

Instrumentation

Synchrotron Radiation Source

10.1080/08957959208206321

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Citations (9)

Superionicity of Hδ− in LaH10 superhydride

Physical review. B./Physical review. B (2023)

Maélie Caussé Grégory Geneste Paul Loubeyre

Recent computational studies have successfully predicted the dramatic uptake of hydrogen by metals under pressure leading to the formation of superhydrides, now ubiquitously observed. ${\mathrm{LaH}}_{10}$ exemplifies the properties of these novel H-rich compounds, some of which form a novel class of superconducting materials. We show here another remarkable property for superhydrides, namely, ${\text{H}}^{\ensuremath{\delta}\ensuremath{-}}$ superionicity. By means of ab initio molecular dynamics simulations in ${\mathrm{LaH}}_{10}$, an exceptionally high hydride $({\mathrm{H}}^{\ensuremath{\delta}\ensuremath{-}})$ diffusion coefficient is calculated at high temperature, with $D=1.7\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}4}\phantom{\rule{0.28em}{0ex}}\mathrm{cm} {}^{2}$/s at 170 GPa and 1500 K, corresponding to an ionic conductivity of $\ensuremath{\sigma}=0.9\phantom{\rule{0.16em}{0ex}}{(\mathrm{\ensuremath{\Omega}}\phantom{\rule{0.16em}{0ex}}\mathrm{cm})}^{\ensuremath{-}1}$ and so indicating a superionic phase. The superionic phase is surprisingly stable up to 2500 K and its melting temperature is remarkably high, similar to that of pure La. The connected path for the hydride ionic diffusion is disclosed, with the H sublattice keeping its clathrate structure. The conductivity properties of ${\mathrm{LaH}}_{10}$ are discussed in relation to the recently discovered family of compounds showing fast pure hydride ions transport.

10.1103/physrevb.107.l060301

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Citations (14)

Evolution with pressure of the hcp-fcc phase transition in solid 4He

Physics Letters A (1987)

Paul Loubeyre

Line (geometry)

10.1016/0375-9601(87)90101-0

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Citations (1)

Three-body exchange interaction in dense helium

Physical Review Letters (1987)

Paul Loubeyre

Self-consistent phonon and Monte Carlo calculations show that the three-body exchange interaction is important in dense helium. Together with a realistic pair potential and the Axilrod-Teller three-body dispersion interaction, it brings calculations into agreement with the experimental equation of state. This interaction stabilizes the hcp structure for pressures greater than about 60 GPa. A speculative phase diagram of high-pressure helium is proposed.

Exchange interaction

Isotopes of helium

10.1103/physrevlett.58.1857

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Citations (98)

Static compression of LiH to 250 GPa

Physical Review B (2012)

Amy Lazicki Paul Loubeyre F. Occelli Russell J. Hemley Mohamed Mézouar

The equation of state of LiH was extended to 252 GPa ($V/{V}_{0}=32%$) at room temperature using x-ray diffraction in diamond-anvil cells. LiH was shown to remain in the the NaCl ($B$1) structure under these conditions, and the predicted $B1$-$B2$ phase transition well known in neighboring alkali halides was not observed. Raman spectroscopy performed up to 120 GPa revealed all transverse and acoustic phonon modes at the $X$ point of reciprocal space. The structural, equation of state and thermodynamic properties clarified in this study enable the benchmarking of current theoretical models.

10.1103/physrevb.85.054103

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Citations (29)