Density Functional Theory study of oxygen clathrate hydrates

Abstract

Interaction energy and vibrational Raman spectra associated with the occupancy of oxygen molecules in dodecahedron (512) and hexakaidecahedron (51264) water cages of the sII hydrate lattice have been studied. The interaction energy shows the 5 12(O2) and 51264(O2) 2 cages to be most stable. The spectral properties validate the most stable occupancy as observed from the interaction energy and show the following trends: The vibrational modes of water molecules in the 512(O 2) cage are red shifted relative to the 512 cage, whereas, the modes in the 512(O2)2 cage are blue shifted relative to the 512(O2) cage. The vibrational modes of water molecules in the 51264(O2) and 51264(O2)2 cages show a red shift relative to the 51264 and 5126 4(O2) cages respectively, although the modes in the 5 1264(O2)3 cage is blue shifted relative to the 51264(O2)2 cage.