Guest-host and guest-guest energy coupling were examined for both the vibrating and rigid lattices. The effect of the vibrating lattice, acting as a thermalizing heat bath, was greater than the mutual thermalization of diffusing guest molecules. This was seen from the decay of the kinetic energy autocorrelation function. However, the mutual thermalization also led to marked relaxation effects. The effect of lattice vibrations upon the self-diffusion of guest molecules was investigated here. Even in the case of small zeolite cavities (cation-free LTA zeolite), with windows of the size of a guest molecule (methane), the effect of the lattice vibrations upon the self-diffusion coefficient was negligible. Variations in the interaction parameters and temperatures, as well as in the elastic force constants of the lattice, led to the conclusion that the diffusion coefficient was quite stable with regard to the effect of lattice vibrations.

Equilibration of the Kinetic Energy in Small Zeolite Cavities. S.Fritzsche, R.Haberlandt, M.Wolfsberg: Chemical Physics, 2000, 253[2-3], 283-94