ABINITIO STUDY OF INTERMOLECULAR POTENTIAL FOR ARHCL

The combination of supermolecular Moller-Plesset treatment with the perturbation theory of intermolecular forces is applied in the analysis of the potential energy surface of ArHCl. Two minima have been found, a primary for collinear Ar-HCl and a secondary for collinear Ar-ClH. The depths of these minima are about 12% below the empirical estimates, due to basis set unsaturation of the dispersion contribution. The Ar-HCl structure is favored by the induction and dispersion terms whereas Ar-ClH by the exchange-repulsion term. The total ab initio potential, as well as its components, are compared with related terms of recent Hutson's H6(3) potential [J. Chem. Phys. 89, 4550 (1988)] and the anisotropy of interaction is analyzed. It is concluded that the one-center multipole expansions of induction and dispersion contributions do not reproduce the correct anisotropy of induction and dispersion terms. Ab initio estimates of three-body effects in the Ar2HCl complex are also discussed.