Properties of<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mrow><mml:msub><mml:mrow><mml:mi mathvariant="normal">H</mml:mi></mml:mrow><mml:mrow><mml:mn>2</mml:mn></mml:mrow></mml:msub></mml:mrow></mml:math>under strong compression in a Ne matrix

Loubeyre, P.; LeToullec, R.; Jp, Pinceaux

doi:10.1103/physrevlett.67.3271

Cited by 23 publications

(14 citation statements)

References 20 publications

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“…In this regime, demixing is not driven by metallization of hydrogen, which is at odds with Lorenzen et al conclusion. In fact, our calculations predict an immiscibility temperature that agree very well with the model calculations of Schouten et al 8 around 50 GPa, and are consistent with an extrapolation to the experimental measurements of Loubeyre et al 7 at 8 GPa.…”

Section: B H-he Miscibility At Low Pressuresupporting

confidence: 79%

“…At relatively low pressures, demixing in the H 2 -He mixture was observed in experiments at room temperature by Streett up to 10 kbar 5 , by van den Bergh and Schouten up to 75 kbar 6 and by Loubeyre et al up to 80 kbar 7 . Subsequent Gibbs ensemble Monte-Carlo calculations with interaction potentials that were used by Schouten et al 8 to predict helium demixing up to 2500 K and 1 Mbar are consistent with the room temperature experimental measurements.…”

Section: Introductionmentioning

confidence: 95%

“…The aim of this paper is to explore the impact of this assumption. We use a similar approach as described in our previous work 12 using thermodynamic integration to account for any non-ideal entropy of mixing and obtain a critical temperature for helium demixing that is consistent with early experimental work [5][6][7] .…”

Section: Introductionmentioning

confidence: 99%

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Hydrogen-helium demixing from first principles: From diamond anvil cells to planetary interiors

et al. 2013

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An accurate determination of the immiscibility of helium in hydrogen has a direct impact on the understanding of the interior structure and of the evolution of Jovian planets. We extend our previous work on hydrogen-helium mixtures (Ref. 12 ) to lower pressures and lower temperatures, across the molecular dissociation regime in hydrogen, to the low pressure molecular liquid. Using density functional theory-based molecular dynamics together with thermodynamic integration techniques, we calculate the Gibbs free energy of the dense liquid as a function of pressure, temperature, and composition. We address the importance of the non-ideal entropy of mixing in the solubility of helium in hydrogen and find that it is critically important in the molecular regime. The resulting demixing temperatures smoothly connect measurements done in diamond anvil cells to the high temperature and pressure conditions found in giant planet interiors.

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Section: B H-he Miscibility At Low Pressuresupporting

confidence: 79%

Section: Introductionmentioning

confidence: 95%

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Hydrogen-helium demixing from first principles: From diamond anvil cells to planetary interiors

et al. 2013

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“…The highest frequency branch agrees closely in frequency and is likely shared (both Raman-and IR-active), whereas the lower frequency branches may be ascribed to different modes. All observed modes are blueshifted with respect to pure H 2 due to partial suppression of the vibrational coupling, as observed in other H 2 /rare gas compounds [23][24][25] . In addition, the H 2 rotational mode near 600 cm À 1 is seen to persist to 50 GPa, confirming that hydrogen remains rotationally free, in contrast to its N 2 host lattice ( Supplementary Fig.…”

Section: Binary Phase Diagrammentioning

confidence: 70%

Pressure-induced chemistry in a nitrogen-hydrogen host–guest structure

et al. 2014

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New topochemistry in simple molecular systems can be explored at high pressure. Here we examine the binary nitrogen/hydrogen system using Raman spectroscopy, synchrotron X-ray diffraction, synchrotron infrared microspectroscopy and visual observation. We find a eutectic-type binary phase diagram with two stable high-pressure van der Waals compounds, which we identify as (N 2 ) 6 (H 2 ) 7 and N 2 (H 2 ) 2 . The former represents a new type of van der Waals host-guest compound in which hydrogen molecules are contained within channels in a nitrogen lattice. This compound shows evidence for a gradual, pressure-induced change in bonding from van der Waals to ionic interactions near 50 GPa, forming an amorphous dinitrogen network containing ionized ammonia in a room-temperature analogue of the Haber-Bosch process. Hydrazine is recovered on decompression. The nitrogen-hydrogen system demonstrates the potential for new pressure-driven chemistry in high-pressure structures and the promise of tailoring molecular interactions for materials synthesis.

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“…The sound velocity in a mixture of nearly equal concentration was measured by Brillouin scattering (Loubeyre 1993c). Increasing deviation from ideality with pressure is observed.…”

Section: 322mentioning

confidence: 99%

High Pressure Experiments for Astrophysics

Loubeyre

1994

International Astronomical Union Colloquium

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In the past decade, measurements of the properties of H 2 and He systems at very high pressures have made great progress, now reaching density at the limit of the plasma phase transition of hydrogen. The potentialities and limits of static and dynamic methods will be reviewed. Then, a survey of the major experimental results is presented. It is the intention of this article to show how these measurements can bring information to model low-mass astrophysical objects. Three levels of usefulness are distinguished on selected examples: data for codes of planetary interiors, constraints for theoretical descriptions of dense matter, observations of unsuspected properties at very high density. AbstractDe grands progres ont ete faits ces dix dernieres annees dans la mesure des proprietes des systemes d^ et d*He sous tres fortes pressions. Des densites a la limite de la transition de phase plasma de lliydrogene peuvent maintenant etre obtenues en laboratoire. Les possibilites et limites des methodes dynamiques et statiques seront tout d'abord discutees. Ensuite, les principaux resultats experimentaux seront presentes. Le but de cet article est de montrer comment ces etudes peuvent etre utiles a la modelisation des interieurs planetaires. Trois niveaux d'application seront degages: donnees pour les codes de structures internes; contraintes pour valider les descriptions theoriques; mise en evidence a tres haute densite de comportements inhabituels .

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Properties ofH2under strong compression in a Ne matrix

Cited by 23 publications

References 20 publications

Hydrogen-helium demixing from first principles: From diamond anvil cells to planetary interiors

Hydrogen-helium demixing from first principles: From diamond anvil cells to planetary interiors

Pressure-induced chemistry in a nitrogen-hydrogen host–guest structure

High Pressure Experiments for Astrophysics

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