Xenon Diffusion in Zeolite NaY:  Transition-State Theory with Dynamical Corrections

The diffusion coefficient for xenon in zeolite NaY at infinite dilution is calculated at low temperatures within a hopping model based on cage-to-cage migration only. Diffusion is modeled as a sequence of jump events that may consist of several barrier passages. The number of jump events is calculated from transition-state theory using the potential of mean force as a basis. The potential of mean force is more or less independent of temperature. In the conversion of the jump rate to the diffusion coefficient, dynamical corrections are taken into account. The mean number of barrier passages per jump event increases significantly when the temperature is raised. However, the contribution of the dynamical corrections to the activation energy remains small. In the range from 140−210 K, the diffusion coefficients obtained from the hopping-model are in excellent agreement with corresponding data from conventional MD simulations.