The quantum-mechanical diffusion constants for H diffusion in a 1-dimensional lattice were investigated by means of the path-integral evaluation of flux-flux correlation functions. Attention was concentrated upon the quantum effect and upon the influence of thermal fluctuations of the substrate atoms; as treated classically. On the basis of the results, it was concluded that the quantum effect upon H diffusion was relatively small and that diffusion occurred by thermal hopping; even at low temperatures. It was suggested that a cross-over from thermally activated hopping to phonon-assisted tunnelling was more likely to occur in body-centered cubic metals than in face-centered cubic metals.

Y.Kaneko: Journal of the Physical Society of Japan, 1995, 64[6], 2235-6