Methane clathrate hydrates: Melting, supercooling and phase separation from molecular dynamics computer simulations

The melting of structure I methane clathrate hydrate has been investigated using NVT molecular dynamics simulations, for a number of potential energy models for water and methane. The equilibrated hydrate crystal has been heated carefully from 270 K, in steps of 5 K, until a well defined phase instability appears. At a density of 0.92 g cm(-3), an upper bound for the mechanical stability of the methane hydrate lattice over a timescale of 11 nanoseconds is 330 R. Finite size effects have been investigated by simulating systems of 1 and 8 units cells of methane hydrate. The properties of the melted system upon cooling are examined.