Theory of high pressure hydrogen, made simple

Phase I of hydrogen has several peculiarities. Despite having a close-packed crystal structure, it is less dense than either the low temperature Phase II or the liquid phase. At high pressure, it transforms into either phase III or IV, depending on the temperature. Moreover, spectroscopy suggests th...

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Bibliographic Details
Published inarXiv.org
Main Authors Magdau, Ioan B, Balm, Floris, Ackland, Graeme J
Format Paper Journal Article
LanguageEnglish
Published Ithaca Cornell University Library, arXiv.org 30.11.2015
Subjects
Crystal structure
First principles
Liquid phases
Molecular dynamics
Phase transitions
Physics - Computational Physics
Physics - Materials Science
Thermodynamic models
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Summary:Phase I of hydrogen has several peculiarities. Despite having a close-packed crystal structure, it is less dense than either the low temperature Phase II or the liquid phase. At high pressure, it transforms into either phase III or IV, depending on the temperature. Moreover, spectroscopy suggests that the quantum rotor behaviour disappears with pressurisation, without any apparent phase transition. Here we present a simple thermodynamic model for this behaviour based on packing atoms and molecules and discuss the thermodynamics of the phase boundaries. We also report first principles molecular dynamics calculations for a more detailed look at the same phase transitions.
ISSN:2331-8422
DOI:10.48550/arxiv.1512.00063