A MPPT2 INVESTIGATION OF THE H2O-CO DIMER - A TEST OF GEOMETRIES, ENERGETICS, AND VIBRATIONAL-SPECTRA

The structure, energetics, and vibrational properties of complexes bet ween water and carbon monoxide have been investigated by second-order perturbation theory. The two previously accounted stable minima H2O-CO and H2O-OC have been studied employing several different basis sets i n order to establish the basis-set dependent fluctuations of the compu ted molecular properties. The complexes are formed via an almost linea r hydrogen bond, where carbon monoxide attached from the carbon end re presents the most stable complex. The importance of electron correlati on is emphasized due to the correlation-induced sign reversal of the C O dipole moment. Substantial perturbations in the vibrational fundamen tal modes are predicted upon complexation rising from the hydrogen bon d formation. The perturbation theory of intermolecular forces within t he supermolecular approach is applied in analysis of the interaction e nergy components. The anisotropic behaviour of the energy components a nd the n --> pi electron density delocalization are addressed upon th e interaction.