Dissociation of high-pressure solid molecular hydrogen: a quantum Monte Carlo and anharmonic vibrational study

A theoretical study is reported of the molecular-to-atomic transition in solid hydrogen at high pressure. We use the diffusion quantum Monte Carlo method to calculate the static lattice energies of the competing phases and a density-functional-theory-based vibrational self-consistent field method to...

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Bibliographic Details
Published in:Physical review letters 2014-04, Vol.112 (16), p.165501-165501, Article 165501
Main Authors: Azadi, Sam, Monserrat, Bartomeu, Foulkes, W M C, Needs, R J
Format: Article
Language:English
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Summary:A theoretical study is reported of the molecular-to-atomic transition in solid hydrogen at high pressure. We use the diffusion quantum Monte Carlo method to calculate the static lattice energies of the competing phases and a density-functional-theory-based vibrational self-consistent field method to calculate anharmonic vibrational properties. We find a small but significant contribution to the vibrational energy from anharmonicity. A transition from the molecular Cmca-12 direct to the atomic I41/amd phase is found at 374 GPa. The vibrational contribution lowers the transition pressure by 91 GPa. The dissociation pressure is not very sensitive to the isotopic composition. Our results suggest that quantum melting occurs at finite temperature.
ISSN:0031-9007
1079-7114
DOI:10.1103/physrevlett.112.165501