Abstract published in Advance ACS Abstracts, April 1, 1995. 0022-365419512099-7 1 14$09.0010 oscillator approach will account for guest-water interactions as well as effects of guest movements on the chemical potential of water. In this work we extend these studies to simplified models of some larger molecules filling the large cavity of structure I. As in previous studies guest molecules are still modeled as spherical Lennard-Jones 12-6 particles. Chosen parameters correspond to previously published parameters applied to represent proper- ties of methane, ethane, ethylene, and carbon dioxide. Calcula- tions have been performed for several temperatures in the region of experimentally measured equilibrium between hydrate and ice, Le., up to a temperature of 273.15 K. A brief summary of the theory is given in section 2. The results obtained from the harmonic oscillator approach and the single-particle integrations are summarized in section 3. Cal- culated dissociation pressures for hydrate in equilibrium with ice are presented in section 4 and compared to experimental data. In section 5 we extrapolate these data to the region of hydrate in equilibrium with liquid water and compare derived results with experimental data. In section 6 we present some calculations for binary mixtures. Our conclusions are given in section 7.