The weak interaction potential of Ar-H2S

Ab initio calculations have been carried out to generate a potential energy surface for the Ar-H2S weakly bonded cluster. The surface displays a low energy trough with small barriers for the ''orbit'' of Ar about H2S. Basis set and correlation effects have been analyzed through a series of calculations at different levels, and the feature of a low energy trough seems assured. The nature of this surface has only little to do with electrostatic interaction, and so, a fairly good fit of the nonelectrical part of the potential surface is obtained with atom-atom Lennard-Jones potential terms. With different surface fits and a fully anharmonic analysis of the ground vibrational state, on-average rotational constants were calculated via rigid-body diffusion quantum Monte Carlo. These calculations show that certain intriguing spectroscopic manifestations of deuterium substitution are associated primarily with the trough feature of the surface. (C) 1997 American Institute of Physics.