Ab initio energetics and kinetics study of H_2 and CH_4 in the SI   Clathrate Hydrate
  We present ab initio results at the density functional theory level for the energetics and kinetics of H_2 and CH_4 in the SI clathrate hydrate. Our results complement a recent article by some of the authors [G. Roman-Perez et al., Phys. Rev. Lett. 105, 145901 (2010)] in that we show additional results of the energy landscape of H_2 and CH_4 in the various cages of the host material, as well as further results for energy barriers for all possible diffusion paths of H_2 and CH_4 through the water framework. We also report structural data of the low-pressure phase SI and the higher-pressure phases SII and SH. 
Qi Li, Brian Kolb, Guillermo Roman-Perez, Jose M. Soler, Felix   Yndurain, Lingzhu Kong, D. C. Langreth, and T. Thonhauser
cond-mat.mtrl-sci