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Fluid helium at conditions of giant planetary interiors

Stixrude, L; Jeanloz, R; (2008) Fluid helium at conditions of giant planetary interiors. P NATL ACAD SCI USA , 105 (32) 11071 - 11075. 10.1073/pnas.0804609105.

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Abstract

As the second most-abundant chemical element in the universe, helium makes up a large fraction of giant gaseous planets, including Jupiter, Saturn, and most extrasolar planets discovered to date. Using first-principles molecular dynamics simulations, we find that fluid helium undergoes temperature-induced metallization at high pressures. The electronic energy gap (band gap) closes at 20,000 K at a density half that of zero-temperature metallization, resulting in electrical conductivities greater than the minimum metallic value. Gap closure is achieved by a broadening of the valence band via increased s-p hydridization with increasing temperature, and this influences the equation of state: The Gruneisen parameter, which determines the adiabatic temperature-depth gradient inside a planet, changes only modestly, decreasing with compression up to the high-temperature metallization and then increasing upon further compression. The change in electronic structure of He at elevated pressures and temperatures has important implications for the miscibility of helium in hydrogen and for understanding the thermal histories of giant planets.

Type:Article
Title:Fluid helium at conditions of giant planetary interiors
DOI:10.1073/pnas.0804609105
Keywords:high pressure, metallization, giant planets, gap closure, hybridization, MOLECULAR-DYNAMICS, SHOCK COMPRESSION, LIQUID METALS, HIGH-PRESSURE, HYDROGEN, JUPITER, SATURN, ENERGY, METALLIZATION, SIMULATIONS
UCL classification:UCL > School of BEAMS > Faculty of Maths and Physical Sciences > Earth Sciences

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