Four-Body Cooperativity in Hydrophonic Association of Methane

Recently computer simulations have succeeded in reproducing the spontaneous solidification process of methane hydrate (MH), but it is still unknown why the obtained solid hydrate is not crystalline We survey the effective attraction force between hydrated methane molecules. Solvent-separated tetrahedral (SS4) configuration of four methane molecules stabilizes at around the melting point (MP) of ice by constructing reverse solvation complex structures in which solvent water molecules are coordinated by solute methane molecules. We also show the effective attraction force to form the SS4 configuration is rather short-ranged, and we anticipate that the solidification process of MH in computer simulation is random aggregation prior to crystallization, similar to colloid particles that interact effectively with a short-range force of attraction.