On the thermodynamic stability of clathrate hydrates

The thermodynamic stability of clathrate hydrates is investigated by theoretically examining the free energy of formation of clathrate hydrates encaging propane and argon. The total free energy is divided into several contributions: the interaction between water and guest molecules, the entropic contribution arising from the combinations of cage occupancy, and the free energy due to intermolecular vibrations. The method introduced here removes some of the assumptions of the van der Waals and Platteeuw theory. It is shown that the shift of the vibrational frequency of the host lattice destabilizes the clathrate hydrates thermodynamically. PACS No.: 61.50Ah