Three-dimensional ab initio potential energy surface for He-O2

An interaction potential with vibrational coordinate dependence is presented for the He-O-2(X(3)Sigma (-)(8),) van der Waals complex. The interaction is calculated with the partially spin-restricted open-shell single and double excitation coupled cluster method with perturbative triples [RCCSD(T)] in the supermolecule approach, with correction for the basis set superposition error. The augmented correlation consistent polarized triple zeta basis set is used with an additional set of bond orbitals. The single reference configuration method breaks down at an O-O separation of r approximate to 3.5 a(0). No points with r > 3.1 a(0) are used in the construction of the potential surface. A high quality 120 parameter fit to 754 ab initio points is presented. Special attention is given to the extraction of the long range coefficients. (C) 2000 American Institute of Physics. [S0021-9606(00)30845-5].