The diffusive hopping of interstitial He and H2O in ice was considered using simulations. It was found that there was a strong coupling between localized translational vibrations of the interstitial H2O, and lattice vibrations. The analysis showed that the localized vibrational motion of the interstitial molecule was one of the dominant factors which governed the diffusion mechanism of the molecule in the ice crystal. Molecular Dynamics Studies of Molecular Diffusion in Ice Ih. Ikeda-Fukazawa, T., Horikawa, S., Hondoh, T., Kawamura, K.: Journal of Chemical Physics, 2002, 117[8], 3886-96