POTENTIAL-ENERGY SURFACE FOR INTERACTIONS BETWEEN N-2 AND HE - AB-INITIO CALCULATIONS, ANALYTIC FITS, AND 2ND VIRIAL-COEFFICIENTS

An ab initio potential energy surface (PES) for the interaction of rig id N-2 with He is calculated by supermolecular fourth-order Moller-Ple sset perturbation theory. The computations involve full counterpoise c orrections and large basis sets including bond functions. The 61 ab in itio points on the PES are fitted to a 21-parameter algebraic form wit h an average absolute error of 0.39% and a maximum error less than 1.2 %. The characteristics of the fitted PES are compared with those of pr evious surfaces. Unlike the older surfaces, our PES has the anisotropy thought to be required for a proper description of experimental data. Pressure second virial coefficients are calculated from our surface a nd compared with experimental values. (C) 1996 American Institute of P hysics.