The motion of rare gases adsorbed in silicalite was simulated by using simple Lennard-Jones atom-atom potentials. The silicalite framework was assumed to be rigid and was represented by oxygen atoms. The simulations were carried out in the microcanonical ensemble. Four loadings were considered: infinite dilution and 2, 5 or 9 atoms per unit cell. The diffusion coefficients were computed using the Einstein relation at 200 to 500K. At 300K and for 2 atoms/unit-cell, values of 24, 12 and 2 x 10-9m2/s were obtained for neon, argon and xenon, respectively Values of 2 and 3kJ/mol for the activation energies were derived for neon and argon, and were nearly independent of the loading. For xenon, the activation energy varied from 6kJ/mol at 0 atoms/unit-cell to 3kJ/mol at 9 atoms/unit-cell.

Self-Diffusion of Rare Gases in Silicalite Studied by Molecular Dynamics. El Amrani, S., Vigné-Maeder, F., Bigot, B.: Journal of Physical Chemistry, 1992, 96[23], 9417-21