Dodecahedron Methane Hydrate Cage Structure – An Ab initio Study

Abstract

Comparative study of 5¹² clathrate hydrate cage having different numbers of methane guest molecules encapsulation is carried out by calculating interaction energy, encapsulation energy and thermo-chemical stability parameters using density functional theory-based calculation with B3LYP functional and 6-31G(d) basis set. Nuclear magnetic resonance spectroscopy(NMR), Infrared spectroscopy (IR spectroscopy) and Raman spectroscopy of empty and methane encapsulated 5¹² clathrate hydrate cages, change in Gibbs free energy and methane hydrate formation enthalpy  are predicted at B3LYP/6-31G++(d,p) level. It is concluded from this study that one methane molecule accommodation is most favorable process and theoretically maximum two methane molecules accommodation is possible as per B3LYP/6-31G (d) calculation. The simulation results are in good agreement with experimental values of cage structural properties like cavity radius, bond lengths and angles, methane hydrate formation enthalpy, NMR, Raman and IR spectroscopy.

Keywords: DFT, interaction energy, encapsulation energy, chemical hardness