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Dewaele, Agnès; Eggert, J. H.; Loubeyre, P.; Toullec, R. Le

doi:10.1103/physrevb.67.094112

Cited by 110 publications

(107 citation statements)

References 39 publications

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“…Significant theoretical and observational evidence for phase separation of helium and neon in the hydrogen-rich outer envelopes of giant planets has been reported (1-8), yet questions over the nature and even existence of this phase separation remain (2,42,43). This is in part due to limited direct experimental data on the hydrogen-helium-neon system at the conditions of phase separation: although hydrogen is observed in a metallic state at the interior conditions of giant planets (44), measurements on the electronic character of helium and neon at relevant densities and temperatures have been limited (12,13,17,45). As phase separation may be controlled by the electronic properties of the constituents (1, 2, 4), the present measurements have a direct bearing on this problem.…”

Section: Discussionmentioning

confidence: 99%

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Opacity and conductivity measurements in noble gases at conditions of planetary and stellar interiors

McWilliams

Dalton

Konôpková

et al. 2015

Proc. Natl. Acad. Sci. U.S.A.

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The noble gases are elements of broad importance across science and technology and are primary constituents of planetary and stellar atmospheres, where they segregate into droplets or layers that affect the thermal, chemical, and structural evolution of their host body. We have measured the optical properties of noble gases at relevant high pressures and temperatures in the laserheated diamond anvil cell, observing insulator-to-conductor transformations in dense helium, neon, argon, and xenon at 4,000-15,000 K and pressures of 15-52 GPa. The thermal activation and frequency dependence of conduction reveal an optical character dominated by electrons of low mobility, as in an amorphous semiconductor or poor metal, rather than free electrons as is often assumed for such wide band gap insulators at high temperatures. White dwarf stars having helium outer atmospheres cool slower and may have different color than if atmospheric opacity were controlled by free electrons. Helium rain in Jupiter and Saturn becomes conducting at conditions well correlated with its increased solubility in metallic hydrogen, whereas a deep layer of insulating neon may inhibit core erosion in Saturn.rare gases | extreme conditions | warm dense matter | giant planet | white dwarf

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Section: Discussionmentioning

confidence: 99%

“…Band gaps for noble gases Xe, Ar, and He were estimated at the volume (31,45,49,50) and temperature of optical transformation using experimental (12,13,17,18,31,38,51,52) and theoretical (2,11,30,(39)(40)(41) results (Figs. S4-S7 and SI Text).…”

Section: Methodsmentioning

confidence: 99%

Opacity and conductivity measurements in noble gases at conditions of planetary and stellar interiors

McWilliams

Dalton

Konôpková

et al. 2015

Proc. Natl. Acad. Sci. U.S.A.

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“…The quality of results obtained here with vdW-DF2 for the transition pressure, change in energy and volume between phases, and the bulk modulus are comparable to those reported by recent DMC calculations, which are, however, computationally much heavier than any ab initio calculations with nonlocal functionals. Reference [37] (for ice VII extrapolated to P ¼ 0) and Ref. [38].…”

Section: -2mentioning

confidence: 99%

Dispersion Interactions and Vibrational Effects in Ice as a Function of Pressure: A First Principles Study

Murray

Galli

2012

Phys. Rev. Lett.

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We present a first principles theoretical framework that accurately accounts for several properties of ice, over a wide pressure range. In particular, we show that, by using a recently developed nonlocal van der Waals functional and by taking into account hydrogen zero point motion, one can properly describe the zero temperature equation of state, the vibrational spectra, and the dielectric properties of ice at low pressure and of ice VIII, a stable phase between 2 and 60 GPa. While semilocal density functionals yield a transition pressure from ice XI to VIII that is overestimated by almost an order of magnitude, we find good agreement with experiments when dispersion forces are taken into account. Zero point energy contributions do not alter the computed transition pressure, but they affect structural properties, including equilibrium volumes and bulk moduli. DOI: 10.1103/PhysRevLett.108.105502 PACS numbers: 63.20.dk, 62.50.Àp, 71.15.Mb, 83.80.Nb Ice has an extremely complex phase diagram [1] that has been studied for over a century [2], due to its importance in several disciplines, encompassing physics, chemistry, and earth and atmospheric sciences. However, until about 35 years ago, little was known experimentally about high pressure phases of ice. For example, the first characterization of ice VIII as an antiferroelectric, ordered phase-now known to be stable at low temperature between 2 and 60 GPa-appeared in 1976 [3]. From a theoretical standpoint, the description of the phase diagram and the properties of ice remains a very challenging problem. Recent ab initio calculations [4,5] have reported remarkable progress in describing the equations of state of some ice phases within density functional theory, as well as in computing optical spectra [6,7]. However, no first principles theory has yet successfully predicted with consistent accuracy a wide range of properties encompassing structural, vibrational, and dielectric properties over a broad range of pressures.In this Letter, we focus on ordered ice phases, ice XI, ordered cubic ice I c , and ice VIII. Ice XI and ordered I c are used as models of the stable phase of ice at ambient pressure close to 0 C. We show that a proper account both of dispersion forces and of hydrogen zero point motion are necessary to obtain a consistently accurate description of several properties of ice over a wide pressure range, at low temperature. We thus establish a theoretical framework that can be used to gain insight into the intricate physics of ice as a function of pressure, from first principles.We carried out calculations within density functional theory and compared results obtained with semilocal (PBE [8]) and nonlocal van der Waals (vdW-DF2 [9]) functionals. We used the QUANTUM ESPRESSO package [10] with hard norm-conserving pseudopotentials [11] for both hydrogen and oxygen and a plane-wave energy cutoff of 160 Ry. A 4 Â 4 Â 4 k-point grid was used for each structure.The lattice energies and equilibrium volumes of each phase were calculated by fully relaxing inte...

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“…The parameter A of the obtained linear relationship approaches to 1, and has only variables from the third digit after decimal point. Moreover, we also notice the work by Dewaele et al, 32 in which the refractive index for fluid helium and hydrogen measured by the diamond anvil cell are n He =(1.005±0.001)+0.199ρ [ρ units in g/cm 3 , 0.08<P<11.5 GPa] and n H2 =(0.994±0.003)+1.63ρ [0.3<P<4.9 GPa], respectively. The parameter A is also approximately 1.…”

Section: Resultsmentioning

confidence: 96%

Measurements of the principal Hugoniots of dense gaseous deuterium−helium mixtures: Combined multi-channel optical pyrometry, velocity interferometry, and streak optical pyrometry measurements

Chen²,

Gu³

et al. 2016

AIP Advances

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The accurate hydrodynamic description of an event or system that addresses the equations of state, phase transitions, dissociations, ionizations, and compressions, determines how materials respond to a wide range of physical environments. To understand dense matter behavior in extreme conditions requires the continual development of diagnostic methods for accurate measurements of the physical parameters. Here, we present a comprehensive diagnostic technique that comprises optical pyrometry, velocity interferometry, and time-resolved spectroscopy. This technique was applied to shock compression experiments of dense gaseous deuterium–helium mixtures driven via a two-stage light gas gun. The advantage of this approach lies in providing measurements of multiple physical parameters in a single experiment, such as light radiation histories, particle velocity profiles, and time-resolved spectra, which enables simultaneous measurements of shock velocity, particle velocity, pressure, density, and temperature and expands understanding of dense high pressure shock situations. The combination of multiple diagnostics also allows different experimental observables to be measured and cross-checked. Additionally, it implements an accurate measurement of the principal Hugoniots of deuterium−helium mixtures, which provides a benchmark for the impedance matching measurement technique.

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Measurement of refractive index and equation of state in dense He,H2,H2

Cited by 110 publications

References 39 publications

Opacity and conductivity measurements in noble gases at conditions of planetary and stellar interiors

Opacity and conductivity measurements in noble gases at conditions of planetary and stellar interiors

Dispersion Interactions and Vibrational Effects in Ice as a Function of Pressure: A First Principles Study

Measurements of the principal Hugoniots of dense gaseous deuterium−helium mixtures: Combined multi-channel optical pyrometry, velocity interferometry, and streak optical pyrometry measurements

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