The thermodynamic stability of a clathrate hydrate encaging non-spherical molecules has been investigated by examining the free energy of cage occupancy. In the present study, a generalized van der Waals and Platteeuw theory is extended to treat the rotational motion of guest molecules in clathrate hydrate cages. The vibrational free energy of both guest and host molecules is divided into harmonic and anharmonic contributions. The anharmonic free energy associated with the non-spherical nature of the guest molecules is evaluated as a perturbation from the spherical guest. Predicted thermodynamic properties are compared with measured values. It is shown that this anharmonic contribution is important in the free energy of the hindered rotation of the guests.
ASJC Scopus subject areas
- General Physics and Astronomy
- Physical and Theoretical Chemistry