Kinetic Monte Carlo simulations of benzene diffusion in Na-Y (Si:Al = 2.0) were performed at 200 to 500K. For hopping on a tetrahedral lattice, the analytical formula for D was derived in terms of hopping lengths and times, yielding the simple-cubic relationship, D = 1/6ka2, even though the lattice was very different from simple cubic. The distribution of cage residence times for benzene in Na-Y was calculated, yielding a single exponential decay controlled by the SII→W rate coefficient, even though several processes contributed to inter-cage motion. Exact agreement between mean square displacement slopes and 1/6ka2 was obtained only when using kinetic inter-cage hopping lengths. The latter were found to exceed the static length by as much as 0.54Å.

Diffusion in Zeolites via Cage-To-Cage Kinetics: Modeling Benzene Diffusion in Na-Y. S.M.Auerbach, H.I.Metiu: Journal of Chemical Physics, 1996, 105[9], 3753-60