Structure, lattice dynamics, and guest vibrations of methane and xenon hydrate
Clathrate hydrates are inclusion compounds, in which small guest atoms or molecules are trapped in cages formed by an ice-like host lattice of water molecules. In recent years large deposits of methane hydrate have been found on the oceanic sea floors, leading to a considerable interest in the physical properties of gas hydrates. In the present work the results from elastic and inelastic neutron scattering experiments, inelastic x-ray scattering experiments and lattice dynamical calculations are presentedfor methane and xenon hydrate. The structure of methane hydrate under geological conditions was determined in a high resolution neutron diffraction experiment. The crystallographic parameters of both the guest molecules and the host lattice have thus been obtained. The inelastic neutron scattering experiments focused on the translational vibrations of the guest molecules and atoms inside the cages and on the density of states of the host lattice. The powder averaged dispersion curves were determined for both methane and xenon hydrate in inelastic x-ray scattering experiments.