A quantum theory of atomic diffusion in a model crystal

Jump rate of an interstitial atom is calculated quantum-mechanically in a model crystal which is made of a linear chain of diatomic molecules. Normal modes of the system are exactly determined in order to investigate effects of perturbed lattice vibrations on diffusion processes. These modes play distinct roles depending on their symmetry under reflection about a site of the diffusing atom. At high temperature the rate has two types of activation energy whose physical origins are quite different. If the mass of the atom is sufficiently light, the rate shows strong deviations from the ordinary Arrhenius formula. (auth.)