Computer simulation studies of the structure I clathrate hydrates of methane, tetrafluoromethane, cyclopropane, and ethylene oxide

We report the results of molecular dynamics simulations on the ice clathrates of methane, tetrafluoromethane, cyclopropane, and ethylene oxide. Although the translational phonon density of states of the host lattice are found to be broadly similar, there are subtle differences which can be correlated to the properties of the guests. The simulations also predict low frequency vibrations that are associated with the rattling and liberations of the guest molecules in the hydrate cages. The occurrence of these low frequency modes may be responsible for the lower thermal conductivities of the clathrate hydrates relative to ordinary ices.