The He-OCS van der Waals potential from model calculations: Bound states, stable structures, and vibrational couplings

A large number of relative distances and orientations between the linear OCS molecule and a helium atom are computed using density functional theory at the post-Hartree-Fock level to treat the repulsive and the short-range well regions, while the dispersion interaction and the attractive parts are included via perturbative corrections. The bound states of the van der Waals (vdW) complex are obtained and the geometries of the most stable structures discussed. The interaction dependence on the intermolecular coordinates is also computed and the corresponding vibrationally adiabatic and nonadiabatic terms obtained and analyzed for the nu(3) stretching motion of the nuclei. (C) 2000 American Institute of Physics. [S0021-9606(00)30132-5].