Detailed simulations were made of argon in NaCaA zeolite. Thermodynamic, structural and dynamic properties of the sorbate as a function of temperature were obtained. The calculated properties included site-site radial distribution functions, energy distribution functions, self-diffusion coefficients, power spectra and properties related to cage-to-cage diffusion. The results suggested that the sorbate was delocalized above 300K. Both modes of cage-to-cage diffusion, surface-mediated and centralized diffusion, were associated with negative barrier heights. The rate of cage-to-cage diffusion was surprisingly associated with negative and positive activation energies below and above 500K. The observed differences in the behavior of the rate of cage-to-cage diffusion between Xe-NaY and Ar-NaCaA systems and the nature of the potential energy surface were considered. The presence of sorbate-zeolite interactions resulted in a significant enhancement of the rate of cage-to-cage diffusion and the rate of cage visits. It was shown that the properties which depended upon the long-term behavior, such as the diffusion coefficient and the rate of cage visits, exhibited the expected Arrhenius dependence upon temperature.

Sorbate Properties and Cage-To-Cage Diffusion of Argon in NaCaA: a Molecular Dynamics Study. Yashonath, S., Santikary, P.: Journal of Physical Chemistry, 1993, 97[51] 13778-87