Ab initio study of van der Waals interaction of CO2 with Ar

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Abstract
The ab initiopotential energy surface of the ArCO2 cluster is calculated using the supermolecular Mo/ller–Plesset perturbation theory (S‐MPPT) and dissected into its fundamental components; electrostatic, exchange, induction, and dispersion energies. The surface contains a single minimum for the perpendicular approach of Ar toward the C atom which has a well depth of ∼210 cm−1 at R=6.5 a 0. This value is obtained using an extended basis set supplied with the bond functions and the fourth order supermolecular Mo/ller–Plesset calculations, and is expected to be accurate to within ±5%. The areas of the surface corresponding to the collinear approach of Ar to CO2 contain an extended plateau. The saddle point in this region for R=9.0 a 0 is stabilized by 117 cm−1. The analytical pair potential for Ar–CO2 obtained by fitting to the individual interaction components is provided. The three‐body effects in the related cluster, Ar2CO2, are examined for two configurations of the Ar2CO2 cluster. The overall nonadditivity is dominated by the three‐body dispersion effect; however, the exchange nonadditivity is the most anisotropic. The sources of this anisotropy are discussed.

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