Shock compression data for liquids. II. Condensed hydrogen and deuterium

Dick, Richard D.; Kerley, Gerald I.

doi:10.1063/1.439955

Cited by 59 publications

(17 citation statements)

References 13 publications

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“…The lower pressure data are in agreement with previous experiments (Dick and Kerley, 1980;Nellis et al, 1983a) and at higher pressures they show a compression of ∼ 5, which suggest that hydrogen is more compressible than deuterium. However, the measured temperature is higher in hydrogen by a factor of ∼1.3.…”

Section: Fig 11 (Color Online)supporting

confidence: 82%

The properties of hydrogen and helium under extreme conditions

McMahon¹,

Morales²,

Pierleoni³

et al. 2012

Rev. Mod. Phys.

478

415

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Hydrogen and helium are the most abundant elements in the universe and, in principle, are the simplest elements. Nonetheless, they display remarkable properties under pressure that have fascinated theoreticians and experimentalists for over a century. Recent advances in computational methods have made it possible to elucidate many of these properties. We review some of the computational methods that have been applied to dense hydrogen and helium in recent years, mainly those that perform a simulation directly from the physical picture of electrons and ions; primarily, those based on density functional theory and quantum Monte Carlo methods. We then discuss the predictions from such methods as applied to the phase diagram of hydrogen, including the solid and fluid phases, with particular focus on the crystal structures, the liquidliquid transition and comparison of the results with experimental shock-wave data. We then discuss predictions of ordered quantum states, including a possible low-temperature fluid and high-temperature superconductivity in the atomic state. We also briefly discuss pure helium, and then focus on hydrogen-helium mixtures, with particular focus on properties of relevance to planetary science.

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Section: Fig 11 (Color Online)supporting

confidence: 82%

The properties of hydrogen and helium under extreme conditions

McMahon¹,

Morales²,

Pierleoni³

et al. 2012

Rev. Mod. Phys.

478

415

View full text Add to dashboard Cite

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“…This leads to the well-known A expansion of the free energy [62]. The first nonvanishing term of the expansion I eads (23) Pli Pl .…”

Section: The Quantum Correction I'mentioning

confidence: 96%

“…Only one of these is of interest to us: tal data is drawn from Refs. [22] (squares) and [23] (circles). The solid curve shows the theoretical Hugoniot curve derived from the model given by Eq.…”

Section: Gl Computation Of the Chemical Equilibriummentioning

confidence: 98%

Fluid hydrogen at high density: Pressure dissociation

1991

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We develop a model for the Helmholtz free energy of fluid hydrogen at high density and high temperature. This model aims at describing both pressure and temperature dissociation and ionization and bears directly on equations of state of partially ionized plasmas, as encountered in astrophysical situations and high-pressure experiments. This paper focuses on a mixture of hydrogen atoms and molecules and is devoted to the study of the phenomenon of pressure dissociation at finite temperatures. In the present model, the strong interactions are described with realistic potentials and are computed with a modified Weeks-Chandler-Andersen fluid perturbation theory that reproduces Monte Carlo simulations to better than 3%%u~. Perturbations of the internal partition functions of H and H2 arising in the nonideal fluid are treated self-consistently with a recently developed occupation probability formalism. Theoretical Hugoniot curves derived from our model are in excellent agreement with experimental data. Pressure dissociation occurs over a narrow density range above 0.5 g/cm' and is remarkably temperature insensitive. Molecules remain the dominant species even at high densities. PACS number(s): 52.25.Jm, 64.30.+t, 05.70.Ce, 65.50.+ m j.INTRODUCTION The past decade has seen tremendous progress in our understanding of dense matter physics, on both the experimental and theoretical fronts. Dynamic compression experiments have revealed exciting new phenomena, such as pressure dissociation in (N2) [1,2], an increase of conductivity upon compression in an initially insulating material (Oz) [3], and they have probed intermolecular potentials down to separations as small as 1.5 A. In particular, experiments on hydrogen and deuterium have determined the H2-Hz interaction potential at high densities [4]Cryogenic samples of solid molecular hydrogen have been compressed to pressures of about 2.5X10 atm, revealing a phase transition in the molecular solid and evidence for reduction of the band gap at the highest pressure reached [5 -7]. This last phenomenon holds the promise of observing the much sought after metallic state of hydrogen in the near future.On the other hand, the recent discovery of global oscillations in Jupiter [8] as well as the achievements of helioand astero-seismology [9,10] give us new information on the interior structure of stars and giant planets, and consequently on the properties of matter under extreme thermodynamic conditions. They offer a unique chance to probe the accuracy of the theoretical models and stress the need for improved equations of state (EOS), particularly in the regime of partial ionization. Indeed, pressure ionization, as well as molecular dissociation, represents a thorny problem in modeling the properties of dense matter. Important advances in statistical physics over the last decade offer the opportunity for significant improvements in our comprehension of this poorly understood phenomenon.Most of the extensive theoretical work on hydrogen has focused on the zero-temperature isotherm whe...

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“…Shock Hugoniot ͑pressure-volume͒ and temperature data have also been measured for fluid deuterium and hydrogen. [23][24][25][26][27][28] Hydrogen is of great importance for planetary science because its cosmological abundance is about 90 at. %.…”

Section: Introductionmentioning

confidence: 99%

Minimum metallic conductivity of fluid hydrogen at 140 GPa (1.4 Mbar)

1999

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Electrical conductivity measurements indicate that fluid hydrogen achieves the minimum conductivity of a metal at 140 GPa, ninefold initial liquid-H 2 density, and 2600 K. Metallization density is defined to be that at which the electronic mobility gap E g is reduced by pressure to E g ϳk B T, at which point E g is filled in by fluid disorder to produce a metallic density of states with a Fermi surface and the minimum conductivity of a metal. High pressures and temperatures were obtained with a two-stage gun, which accelerates an impactor up to 7 km/sec. A strong shock wave is generated on impact with a holder containing liquid hydrogen at 20 K. The impact shock is split into a shock wave reverberating in hydrogen between two stiff Al 2 O 3 anvils. This compression heats hydrogen quasi-isentropically to about twice its melting temperature and lasts ϳ100 ns, sufficiently long to achieve equilibrium and sufficiently short to preclude loss of hydrogen by diffusion and chemical reactions. The measured conductivity increases four orders of magnitude in the range 93 to 140 GPa and is constant at 2000 ͑⍀ cm͒ Ϫ1 from 140 to 180 GPa. This conductivity is that of fluid Cs and Rb undergoing the same transition at 2000 K. This measured value is within a factor of 5 or less of hydrogen conductivities calculated with ͑i͒ minimum conductivity of a metal, ͑ii͒ Ziman model of a liquid metal, and ͑iii͒ tight-binding molecular dynamics. At metallization this fluid is ϳ90 at. % H 2 and 10 at. % H with a Fermi energy of ϳ12 eV. Fluid hydrogen at finite temperature undergoes a Mott transition at D m 1/3 a*ϭ0.30, where D m is the metallization density and a* is the Bohr radius of the molecule. Metallization occurs at a lower pressure in the fluid than predicted for the solid probably because crystalline and orientational phase transitions in the ordered solid do not occur in the fluid and because of many-body and structural effects. Tight-binding molecular dynamics calculations by Lenosky et al. suggest that fluid metallic hydrogen is a novel state of condensed matter. Protons are paired transiently and exchange on a timescale of a few molecular vibrational periods, ϳ10 Ϫ14 sec. Also, the kinetic, vibrational, and rotational energies of the dynamically paired protons are comparable. ͓S0163-1829͑99͒02805-2͔

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Shock compression data for liquids. II. Condensed hydrogen and deuterium

Cited by 59 publications

References 13 publications

The properties of hydrogen and helium under extreme conditions

The properties of hydrogen and helium under extreme conditions

Fluid hydrogen at high density: Pressure dissociation

Minimum metallic conductivity of fluid hydrogen at 140 GPa (1.4 Mbar)

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