Ab initio potentials for weakly interacting systems: Homonuclear rare gas dimers

A series of high-level ab initio interatomic potentials for the homonuclear rare gas dimers He-2, Ne-2, and Ar-2 is presented, with predictions of rovibrational spectroscopic parameters and second virial coefficients. These potentials were created by using d-aug-cc-pVnZ, n = D,T,Q basis sets, NP4 and CCSD(T) correlation energy treatments, the counterpoise correction to the basis set superposition error, and extrapolation schemes for estimating complete basis set (CBS) limits. A careful FCI correction was added to our best He-2 CCSD(T) potential. The characteristic parameters D-e, R-e, k, and sigma of the ab initio potentials were compared with those of reliable empirical and ab initio potentials. Our best results for He-2 recovered 99.9% of Janzen's SAPT2 well depth. In the case of Ar-2, we recovered 99.8% of Aziz's HFDID1 well depth. For neon, second virial coefficients typically came to within 0.5-1.0 cm(3)mol(-1) of experimental values and rovibrational energy levels exhibited errors of about 1.4 cm(-1). Our best argon results exhibited second virial coefficients in agreement of 0.25 cm(3)mol(-1) with experiment and rovibrational energy level errors around 0.2 cm(-1). (C) 2003 Wiley Periodicals, Inc.