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How methane hydrate recovers at very high pressure the hexagonal ice structure

Abstract : Methane hydrate was recently shown, both experimentally and through simulations, to be stable up to the remarkably high pressure of 150 GPa. A new methane hydrate high-pressure (MH-IV) phase, reminiscent of ice at ambient pressure, was described for pressures above approximately 40 GPa. We disentangle here the main contributions to the relative stability of the lower pressure, denoted MH-III and the high-pressure MH-IV structures. Through several simulation techniques, including metadynamics and Path Integral Molecular Dynamics for nuclear quantum effects, we analyze the phase transition mechanism, which implies hydrogen bond breaking and reforming, as well as methane reordering. The transition pathway is far from trivial and the quantum delocalization of the hydrogen nuclei plays a significant role.
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https://hal.archives-ouvertes.fr/hal-03029341
Contributor : Fabio Finocchi Connect in order to contact the contributor
Submitted on : Saturday, November 28, 2020 - 12:15:48 PM
Last modification on : Monday, June 14, 2021 - 10:03:29 AM

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S. Schaack, Ph. Depondt, M. Moog, F. Pietrucci, Fabio Finocchi. How methane hydrate recovers at very high pressure the hexagonal ice structure. Journal of Chemical Physics, American Institute of Physics, 2020, 152 (2), pp.024504. ⟨10.1063/1.5129617⟩. ⟨hal-03029341⟩

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