Intermolecular potential energy surface of the water-carbon dioxide complex

A complete intermolecular potential energy surface (PES) of the H2O-CO2 complex has been constructed using a large scale ab initio calculations. This PES was sampled at 23 000 points of a five dimensional configuration space of the intermolecular coordinates. The interaction energy was calculated using the second order Moller-Plesset perturbation method in conjunction with the standard aug-cc-pVTZ basis set supplemented by bond functions. Single-point energy values were used to construct the analytical many-body representations of the PES that was further improved using a set of the interaction energy values calculated along the one-dimensional cuts of PES by employing the coupled cluster singles and doubles including connected triples method. The accurate data on the structure and energetics of the complex considered have been reported. The analysis of the PES determined revealed its complex structure. A few bifurcations were found on the minimum energy paths along the coordinates describing the radial and angular motions. For the torsional motion, four symmetrically equivalent potential barriers were found as a consequence of the bifurcations, so earlier models of this motion assuming two equivalent potential barriers were justified only for the lowest torsional states. (C) 2010 American Institute of Physics. [doi: 10.1063/1.3439693]