Ab initio basis set study of the CO center dot center dot center dot He van der Waals interaction

The ab initio potential energy surface for the weakly bound van der Waals C O He has been performed in the framework of the supermolecule approach, usi ng fourth order Moller-Plesset perturbation theory with different basis set s, constructed to give accurate values for the electric moments and polariz abilities, supplemented by bond functions placed at the midpoint along the line joining He with the center of mass of CO. All atom-centered basis sets explored in the present study predict single-minimum near collinear C-O .. . He optimum structures. Near T-shaped optimum structures are predicted whe n these basis sets are augmented with a set of bond functions located in th e middle of the van der Waals bond, in agreement with recent experimental a nd ab initio potentials. (C) 1999 Elsevier Science B.V. All rights reserved .