Metallization of fluid hydrogen

Nellis, W. J.; Louis, Ard A.; Ashcroft, N. W.

doi:10.1098/rsta.1998.0153

Cited by 49 publications

(40 citation statements)

References 50 publications

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“…The unexpected compression was not incompatible with some existing theoretical predictions and models which allowed for molecular dissociation. Note that at sufficiently high pressure, the compression on the principal Hugoniot must attain the ideal gas value of 4 (Nellis, 2006a). Along the Hugoniot the system was observed, by optical reflectivity measurements (Celliers et al, 2000), to undergo a continuous insulator to metal transition in the region between 17 GPa to 50 GPa as inferred by a continuous increase in the reflectance signal (from 10% to 50%) and a saturation at higher pressures.…”

Section: Fig 11 (Color Online)mentioning

confidence: 99%

The properties of hydrogen and helium under extreme conditions

McMahon¹,

Morales²,

Pierleoni³

et al. 2012

Rev. Mod. Phys.

485

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)mentioning

confidence: 99%

The properties of hydrogen and helium under extreme conditions

McMahon¹,

Morales²,

Pierleoni³

et al. 2012

Rev. Mod. Phys.

485

415

View full text Add to dashboard Cite

show abstract

“…On active carbon with the specific surface area of 1,315 m -2 g -1 , 2 mass% hydrogen is reversibly adsorbed at a temperature of 77 K (ref. 4). On nanostructured graphitic carbon at 77 K (liquid nitrogen temperature), the reversibly adsorbed quantity of hydrogen correlates with the specific surface area of the sample.…”

Section: Hydrogen Adsorption On Solids Of Large Surface Areamentioning

confidence: 99%

“…The continuously evaporated hydrogen may be catalytically burnt with air in the overpressure safety system of the container or collected again in a metal hydride. (Solid hydrogen is a molecular insulating solid; under high pressure it transforms into metallic, possibly even superconducting hydrogen 4 with T c of 200-300 ᑻC.) Cryotechniques for cooling and superinsulated low temperature storage units were developed and proven in space technology.…”

Section: Conventional Hydrogen Storagementioning

confidence: 99%

Hydrogen-storage materials for mobile applications

Schlapbach

Züttel

2001

Nature

7,872

4,566

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Energy can be stored in different forms: as mechanical energy (for example, potential energy or rotation energy of a flywheel); in an electric or magnetic field (capacitors and coils, respectively); as chemical energy of reactants and fuels (batteries, petrol or hydrogen); or as nuclear fuel (uranium or deuterium). Chemical and electric energy can be transmitted easily because they both involve electronic Coulomb interaction. Chemical energy is based on the energy of unpaired outer electrons (valence electrons) eager to be stabilized by electrons from other atoms. The hydrogen atom is most attractive because its electron (for charge neutrality) is accompanied by only one proton. Hydrogen thus has the best ratio of valence electrons to protons (and neutrons) of all the periodic table, and the energy gain per electron is very high.Hydrogen is the most abundant element on Earth, but less than 1% is present as molecular hydrogen gas H 2 . The overwhelming majority is chemically bound as H 2 O in water and some is bound to liquid or gaseous hydrocarbons. The clean way to produce hydrogen from water is to use sunlight in combination with photovoltaic cells and water electrolysis (see review in this issue by Grätzel, pages 338-344). Other forms of primary energy and other water-splitting processes are also used: the hydrogen consumed today as a chemical raw material (about 5 ǂ10 10 kg per year worldwide) is to a large extent produced using fossil fuels and the reaction of hydrocarbon chains (-CH 2 -) with H 2 O at high temperatures, which produces H 2 and CO 2 . Direct thermal dissociation of H 2 O requires temperatures higher than 2,000 ᑻC (>900 ᑻC with a Pt/Ru catalyst).The chemical energy per mass of hydrogen ) is at least three times larger than that of other chemical fuels (for example, the equivalent value for liquid hydrocarbons is 47 MJ kg -1 ). Once produced, hydrogen is a clean synthetic fuel: when burnt with oxygen, the only exhaust gas is water vapour, but when burnt with air, lean mixtures have to be used to avoid the formation of nitrogen oxides. Whether hydrogen can be considered a clean form of energy on a global scale depends on the primary energy that is used to split water 1 . The availability of free energy is often unsafe. The mechanical energy of a 1,000-kg car running out of control at 40 km h -1 can kill pedestrians. The process of burning hydrogen can be done in an efficient and controlled way to liberate energy at a desirable rate, or in an uncontrolled way with the potential to cause damage. For historical reasons hydrogen has a bad reputation, which is not altogether justified: a more recent analysis 2 of the Hindenburg catastrophe shows that the air ship caught fire because of a highly flammable skin material and not because of the hydrogen gas it contained. The safety of hydrogen relies on its high volatility and non-toxicity.Today, many scientists and engineers, some companies, governmental and non-governmental agencies and even finance institutions are convinced that hydrogen's physical...

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“…[39][40][41] These states are significantly off the principal Hugoniot and were achieved by using a reverberating shock wave. Since LLNL ICF targets go through this regime and previous shock experiments were done primarily on the Hugoniot, this is a major technological advance.…”

Section: B Molecular Fluidsmentioning

confidence: 99%

Historical Background of Ultrahigh Pressure Shock Compression Experiments at LLNL: 1973 to 2000

Nellis¹

2000

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Metallization of fluid hydrogen

Cited by 49 publications

References 50 publications

The properties of hydrogen and helium under extreme conditions

The properties of hydrogen and helium under extreme conditions

Hydrogen-storage materials for mobile applications

Historical Background of Ultrahigh Pressure Shock Compression Experiments at LLNL: 1973 to 2000

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