Ab initio investigation of the ground potential energy surface of the CO₂⁺·Ar ion

The ground potential energy surface of the CO₂⁺·Ar complex has been investigated by ab initio techniques for C_∞ν, C_2ν, and C_s structures of the ion. The C_∞ν and C_2ν stationary points are found to be transition states which lead smoothly to the global C_s minimum-energy structure. In all three geometries, the interaction between CO₂⁺ and Ar is found to be largely electrostatic in nature. The equilibrium geometry of the the CO₂⁺·Ar ion is planar with a near linear OCO moiety and a C-O-Ar angle near 100°. At the QCISD(T)/ aug-cc-pVTZ level of theory, D_e is calculated to be 0.220 eV for dissociation into CO₂⁺ and Ar. Harmonic vibrational frequencies, infrared intensities, and frequency shifts occurring for ¹³C and ¹⁸O calculated at the QCISD/cc-pVDZ (for C and O) and aug-cc-pVDZ (for Ar) level of theory are reported.