Effect of small cage guests on hydrogen bonding of tetrahydrofuran in binary structure II clathrate hydrates.

Molecular dynamics simulations of the pure structure II tetrahydrofuran clathrate hydrate and binary structure II tetrahydrofuran clathrate hydrate with CO(2), CH(4), H(2)S, and Xe small cage guests are performed to study the effect of the shape, size, and intermolecular forces of the small cages guests on the structure and dynamics of the hydrate. The simulations show that the number and nature of the guest in the small cage affects the probability of hydrogen bonding of the tetrahydrofuran guest with the large cage water molecules. The effect on hydrogen bonding of tetrahydrofuran occurs despite the fact that the guests in the small cage do not themselves form hydrogen bonds with water. These results indicate that nearest neighbour guest-guest interactions (mediated through the water lattice framework) can affect the clathrate structure and stability. The implications of these subtle small guest effects on clathrate hydrate stability are discussed.