The intermolecular potential energy surface for CO₂-Ar: Fitting to high-resolution spectroscopy of Van der Waals complexes and second virial coefficients

Two potential energy surfaces for CO₂-Ar are obtained by least-squares fitting to the high-resolution spectra of Van der Waals complexes and the second virial coefficients of Ar+CO₂ gas mixtures. The potentials incorporate a repulsive wall based on monomer ab initio calculations and the assumption that the repulsion potential is proportional to the overlap of the monomer charge densities. The dispersion energy is represented in a two-site model, with dispersion centers located along the C-O bonds of CO₂. The resulting potentials give a good representation of all the experimental data with only three or four adjustable parameters. They are quite different from previous empirical CO₂-Ar potentials, which all have either a poor representation of the attractive well or a poor representation of the repulsive wall.