Equilibration of the kinetic energy in small zeolite cavities: The thermalization effect of lattice vibrations and of mutual interaction in the diffusion of methane in a cation-free LTA zeolite Original Research Article

The guest–host and the guest–guest energy coupling in a zeolite are examined for both the vibrating and the rigid lattice. Although the effect of the vibrating lattice acting as a thermalizing heat bath is stronger than the mutual thermalization of diffusing guest molecules, as can be seen, for example, from the decay of the kinetic energy auto correlation function this mutual thermalization also leads to remarkable relaxation effects. The influence of lattice vibrations on the self-diffusion of the guest molecules is investigated. Even in the studied case of small zeolite cavities (cation-free LTA zeolite) with windows of the size of a guest molecule (methane), the influence of the lattice vibrations on the self-diffusion coefficient is negligible. Variations of interaction parameters and temperatures as well as of the elastic force constants in the lattice lead to the conclusion that the diffusion coefficient is quite stable to the influence of lattice vibrations.