DEPENDENCE OF DIFFUSION PROPERTIES IN ZEOLITE-Y AND ZEOLITE-A - A SEARCH IN THE SORBATE INTERACTION PARAMETER SPACE

Molecular dynamics simulations have been carried out at room temperatu re on spherical monatomic sorbates in zeolites Y and A. A search has b een made in the sorbate Lennard-Jones epsilon(SS)-sigma(SS) parameter space to see the variation of three properties, namely, rate of interc age diffusion (k(c)), rate of cage visits (k(V)) and diffusion coeffic ient (D). The results suggest that the three properties show a decreas e with increase in epsilon(SS) for all values of sigma(SS) except for k(c) at the value of sigma(SS) corresponding to the tight fit paramete r gamma approximate to 1. These results for k(c) are consistent with e arlier work indicating the existence of a diffusion anomaly or a levit ation effect. The absence of such behaviour on the part of k(V) and D seems to suggest that a diffusion anomaly may be strongly temperature dependent.