We model nonbonded, atomistic guest-guest and guest-host interactions as pairwise additive and with -Leonard-Jones atom-pair potentials truncated at r cutoff " 14.0 Å. We take Lennard-Jones parameters ( : well depth, σ: distance such that potential is zero) for a-a interactions (a denotes a chemical element) from the Universal Force Field (UFF) [ ] and use Lorentz-Berthelot mixing rules to obtain the parameters for a-b interactions (b ‰ a denotes a chemical element).