Vibrational partition functions for atom-diatom and atom-triatom van der Waals systems

The vibrational partition functions of atom-diatom and atom-(linear triatom ) van der Waals complexes are calculated directly within the classical stat istical mechanics formalism by using a Monte Carlo procedure. Constrained c lassical Hamiltonians for these molecular systems have been derived by cons training the internal coordinates of the chemically bound molecules to thei r equilibrium values. The method is applied to the Ar . . . CN and Ar . . . HCN van der Waals molecules, and the results compared with previously repo rted ones.