Theoretical studies of Van der Waals clusters

Abstract

The vibrational energy levels of various rare gas trimers, Ar(_3), Ne(_3), He(_3), Ar(_2)Ne and Ne(_2)Ar, have been calculated using a coupled channel approach. We have compared results obtained with previous calculations. The existence of Efi-mov states in He(_3) has been investigated, and no evidence of their existence has been found. The affect of the Eckart conditions on embedding axis into a rotating-vibrating system has been investigated for several rare gas systems. A wide range of rare gas trimers have been studied, Ar(_3), He(_2)Ar, Ar(_2)He, Ar(_2)Ne and Ne(_2)Ar. For each trimer the full range of molecular motion is investigated. The low energy minima for the Ar(_n)N(_2) and Ne(_n)N(_2) systems have been found using simulated annealing search, and a gradient based minimisation technique, of a pairwise potential energy surface. Clusters with n ≥ 12 have been studied, and first solvation shells for both systems have been proposed. For each value of n, for n = 1 - 12, the first few low energy minima of the potential energy surface have been found. From these studies, we have gained a detailed understanding of the interplay of forces that determine the low energy structures for these systems. The affect of three-body interactions on the low energy minima both rare gas-N(_2) systems has been studied. In both system, rare gas-rare gas and rare gas- threebody interactions have been taken into account. This study has shown that the three-body forces have a small affect on the low energy structures of each system.