LATTICE-RELAXATION IN TYPE-I GAS HYDRATES

Computer simulations have been used to examine the approximations upon which the van der Waals-Platteeuw theory of hydrate stability is based, and in particular, the extent to which the water lattice relaxes about the guest molecules. It is found that the behavior of the water lattice depends significantly on both the nature and number of guest molecules present-an effect that is neglected in the van der Waals-Platteeuw theory. The simulations also indicate an important role for the repulsive guest-host interactions in generating the mechanical stability of gas hydrates in the bulk. On the basis of these simulations, it is conjectured that surface interactions (particularly at a water/guest interface) are fundamental to the phase behavior of gas hydrates.