Mechanisms for Thermal Conduction in Various Polymorphs of Methane Hydrate

Extensive equilibrium molecular dynamics (MD) simulations have been performed to investigate thermal conduction mechanisms via the Green-Kubo approach for fully-occupied type I, II and H methane hydrates. We have shown that the crystal structure of the clathrate framework and damping of guest-host interactions in type I methane hydrate contribute to a lower thermal conductivity vis-à-vis ice Ih and its glass-like temperature dependence. We have found that substantially less damping in guest-host energy transfer is present in type II and H methane hydrate polymorphs at higher temperatures, giving rise to somewhat larger thermal conductivities relative to type I methane hydrate with a more crystal-like temperature dependence.