Methane Hydrate under High Pressure: Searching for Centering of Hydrogen Bonds

TL;DR

This study uses first principles calculations to investigate high-pressure phases of methane hydrate, revealing hydrogen bond ionization and centering at significantly lower pressures than in pure ice, with potential spectroscopic detection methods.

Contribution

It provides new insights into hydrogen bond behavior in methane hydrate under high pressure, highlighting lower transition pressures compared to pure ice.

Findings

Hydrogen ionization occurs around 40 GPa.

Hydrogen bond centering occurs around 70 GPa.

Transitions are detectable via IR/Raman spectroscopy or neutron diffraction.

Abstract

The structural, electronic, and spectroscopic properties of a high-pressure phase of methane hydrate (MH-III) are studied by first principles electronic structure calculations. A detailed analysis of the atomic positions suggests that {\it ionization} of hydrogen-bonded water molecules occurs around 40GPa and {\it centering} or symmetrization of hydrogen-bonds occurs around 70 GPa. These pressures are much lower compared with ioninzation around 55 GPa and centering around 100 GPa in pure ice. The transition may be observed with low-temperature IR/Raman spectroscopy of OH stretching modes or neutron diffraction.