An efficient Monte Carlo algorithm for simulating diffusion in tight-fitting host-guest systems, based upon using zeolite normal modes was developed and applied. Computational efficiency was gained by sampling framework distortions using normal-mode coordinates, and by exploiting the fact that zeolite distortion energies were well approximated by harmonic estimates. Additional savings were achieved by performing local normal-mode analyses, thus focusing the calculations on zeolite distortions relevant to guest diffusion.

Calculating Free Energies for Diffusion in Tight-Fitting Zeolite-Guest Systems: Local Normal-Mode Monte Carlo. S.C.Turaga, S.M.Auerbach: Journal of Chemical Physics, 2003, 118[14], 6512-7