Elastic properties of methane hydrate at high pressures

Abstract

The longitudinal acoustic phonon dispersion of high-pressure methane hydrate structures MH-II and MH-III was determined by in situ high-pressure inelastic x-ray scattering. These results on powder samples, in conjunction with the previously established equation of state, allowed the derivation of the aggregate compressional and shear sound velocity, as well as the effective elastic and shear modulus. The elastic properties were found to differ substantially from the elastic properties of high pressure ice structures, while strongly reflecting the transition from a cage clathrate (MH-II) to a filled ice structure (MH-III).