A MOLECULAR-DYNAMICS STUDY OF XENON SORBED IN SODIUM Y-ZEOLITE .1. TEMPERATURE AND CONCENTRATION-DEPENDENCE

The sorption properties of xenon sorbed in sodium Y zeolite as a function of adsorbate concentration and temperature have been obtained from molecular dynamics simulations. The properties reported include the various site-site and center of cage-center of mass radial distribution functions, distribution of guest-host energy, guest-guest pair and bonding energy, self-diffusion coefficients, the power spectra, and the distribution of site residence times. The location of the physical adsorption site for xenon is the same as for methane. The guest-host energy distribution function for xenon differs significantly from the bimodal function observed for methane. It is shown that the mean square displacement shows a crossover from ballistic to diffusive behaviour and the activation energy for diffusion is 4.1 kJ/mol. We suggest that the 15-cm-1 frequency mode seen in the power spectra of the autocorrelation function corresponds to the Xe-Xe dimers. The nonavailability of sorption sites at higher adsorbate concentrations is reflected in the guest-host distribution function, center of cage-center of mass radial distribution function, power spectra, and other properties.