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‐pV n Z, n = D,T,Q basis sets, MP4 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 σ 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 Janzen, A.R.; Aziz, R.A. J Chem Phys 1997, 107, 914–919. In the case of Ar 2 , we recovered 99.8% of Aziz's HFDID1 well depth Aziz, R.A. J Chem Phys 1993, 99, 4518–4525. 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 . © 2003 Wiley Periodicals, Inc. Int J Quantum Chem 95: 303–312, 2003