INTERMOLECULAR VIBRATIONAL FREQUENCIES OF (HF)N AND (HCN)N WEAK COMPLEXES BY ELECTRICAL MOLECULAR MECHANICS

A model of intermolecular interaction based on simple electrical energetics, and recently formulated for molecular mechanics treatment of clusters, has been extended to find harmonic vibrational frequencies and transition moments for the intermolecular modes of clusters. Calculation of these values is helpful for estimating zero-point stability corrections and for distinguishing between strong and weak transitions. Application to certain binary complexes shows good agreement with high level ab initio values of the harmonic frequencies. The approach used in the model calculations is presented along with applications to cyclic complexes of HF, with as many as six monomers, and to linear chains of HCN molecules, up to eight in number. This demonstrates the feasibility of the method for studying intermediate-sized clusters, and where comparison values do exist, this offers an assessment of the reliability. © 1990 American Chemical Society.