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

The ab initio potential 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 a0. 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 a0 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. © 1996 American Institute of Physics. [ABSTRACT FROM AUTHOR]