Details of cage-to-cage migration were obtained from an analysis of the trajectory of a probe adsorbate. It was observed that particles explored the region within a radius of 2Å around the window center, but with diffusion taking place mainly at 1.6Å from the window center with a potential energy of nearly -12kJ/mol. A barrier of about 0.5kJ/mol was observed for surface-mediated diffusion. Surprisingly, for diffusion without surface mediation for a particle going from one cage center to another, there was an attractive well near to the window instead of a barrier. At low adsorbate concentrations and room temperature, the predominant mode for cage-to-cage migration was surface-mediated diffusion. The analysis suggested that particles slid along the surface of the inner walls of the α-cages during migration from one cage to another.

A Molecular Dynamics Study of Cage-To-Cage Migration in Sodium Y Zeolite: Role of Surface-Mediated Diffusion. Yashonath, S.: Journal of Physical Chemistry, 1991, 95[15], 5877-81