Temperature Dependence of Atomic Displacement Distribution in Hydrates Obtained by Powder Neutron Diffraction Experiments

Neutron diffraction is one of the most sensitive methods for analyzing hydrogen（especially deuterium）. Clathrate hydrates have a cage-like hydrogen bonding network that encloses guest molecules. The temperature dependence of atomic displacement parameters in hydrogen networks was investigated using powder neutron diffraction as the scattering-length density distribution. Hydrogen sulfide hydrate has a spread from the line between oxygen atoms, and the scattering-length density distribution changes with temperature. The low-temperature phase of ethane hydrate also has a bent hydrogen bonding between oxygen atoms. These anharmonic distributions arise from the thermal motion of guest molecules and the resulting interactions between them and the host structure.