Molecular Dynamics Simulation Studies of Gas Hydrate Growth with Impingement

Clathrate hydrates have attracted much attention in energy and environment technology as well as the nature of icy bodies. We report a molecular dynamics simulation study of methane hydrate growth with impingement which has not been investigated by either experiment or simulation as far as the authors' knowledge. Several unique features have been discovered including dislocation, two occupied hydrate cages and fast methane diffusion. A certain proportion of hydrate cages were found to be occupied simultaneously by two methane molecules, even in the 5(12)6(2) cage which was thought to be impossible. Methane molecules were demonstrated to hop between two-occupied and one-occupied hydrate cages as well as between gas bubble and nearby hydrate cages when a gas bubble was present. The diffusion rate during the hopping process is in the order of 10(-9) to 10(-8) m(2)/s, which is 3 similar to 4 order of magnitude faster than that during hopping between one-occupied and empty hydrate cages.