Thermodynamic properties of methane clathrate hydrate

Density functional theory calculation has been carried out to elucidate the thermodynamic properties of the methane clathrate hydrate(51262 and 512).At the B3LYP/6-31G**level,methane clathrate hydrate is fully optimized and the potential energy curves are scanned.The theoretical calculations showed that one methane molecule encaged in the 51262 cavity is most stable.The preserved condition for safely storing methane hydrate is 190 K,200 MPa.The calculated values of symmetric C—H stretching frequencies of the methane molecule in the two cluster cavities are agreed with the experimental data.The narrow potential wall in the 512 cavity leads to restricting the motion of the methane molecule in the small cavity.