Ab initio geometry optimizations at MP2/6-31G*//HF/6-31G* level suggested that the CH4(H2O)20 cluster with a CH4 molecule within the (H2O)20 dodecahedral cavity has a stabilization energy of ~ 7 kcal/mole relative to separated CH4 and (H2O)20 molecules. The cavity of a 20 mer fused cubic or edge-shared prismic structure was too small to enclose a CH4 molecule. Even though the (H2O)21 cluster with H2O molecule within the dodecahedral cavity was significantly more stable (~ 28 kcal/mole) than CH4(H2O)20, the dodecahedral cage was too distorted in (H2O)21 to form a fused hydrate structure. The dodecahedral cage remained almost undistorted in CH4(H2O)20 and hence, could form a fused hydrate structure. During a fused structure formation, each pentagonal ring shared by two dodecahedral structures or a dodecahedral and a tetrakaidecahedral structures resulted in stabilization by ~ 20-23 kcal/mole. Original is an abstract.
All Science Journal Classification (ASJC) codes
- Chemical Engineering(all)