Accurate ab initio potential for argon dimer including highly repulsive region

An ab initio potential has been developed for the argon dimer. This potential is based on coupled-cluster calculations with single, double, and non-iterated triple excitations in a sequence of very large basis sets, up to augmented sextuple-zeta quality and containing bond functions, followed by extrapolations to the complete basis set limit. The calculations included intermolecular distances as small as 0.25 angstrom, where the interaction potential is of the order of 4 keV. The computed points were fitted by an analytic expression. The new potential has the minimum at 3.767 angstrom with a depth of 99.27 cm(-1) respectively, very close to experimental values of 3.761 +/- 0.003 angstrom and 99.2 +/- 1.0 cm(-1) respectively. The potential was used to compute the spectra of the argon dimer and the virial coeffcients. The latter calculations suggest a possible revision of the established experimental reference results. From the agreement achieved with experimental values and from comparisons of the fit with available piecewise information on specific regions of the argon - argon interaction, one can assume that the present work provides the best overall representation of the true argon - argon potential to date.