Ab Initio Study of the Intermolecular Interactions in Small Benzene Clusters: The Equilibrium Structures of Trimer, Tetramer, and Pentamer

Abstract

Correlated (MP2) calculations with 6-31G and 6-31G* basis sets have been used to probe the equilibrium geometries of the benzene trimer, tetramer, and pentamer. The lowest energy configuration was found to be a trigonal C3h structure for the trimer and a tetrahedral C3 structure for the tetramer. For the pentamer, the MP2/6-31G calculation yields the lowest energy structure, which is a trigonal bipyramid (C3h). In the tetramer and pentamer, the fourth and fifth benzene molecules occupy the apex of the trigonal bipyramid with their molecular plane perpendicular to the 3-fold symmetry axis of the cyclic trimer motif. These structures, which maximize nearest-neighbor coordination number, suggest manifestation of the Wefelmeier growth sequence in benzene clusters.