Nonadiabatic quantum theory of interstitial diffusion in crystals

The influence of the nonadiabaticity of interstitial motion on the quantum underbarrier diffusion is discussed. The wave functions of crystals with an impurity, localized in initial and final positions, are obtained and used for the calculation of the probability of interstitial transitions from one interstitial to another per unit time. The temperature dependence of this transition probability is analysed, taking into account the nonadiabaticity of impurity motion and the deviation from the Condon approximation which is used for the calculation of transition matrix elements. (author)