Ab initio study of energy, structure and dynamics of the water-carbon dioxide complex

摘要

The supermolecular Moller-Plesset perturbation theory (MPPT) is applied to calculate and analyze selected portions of the potential-energy surface (PES) of the H2O ... CO2 complex. Two kinds of minima have been found. The global minimum, which corresponds to the T-shaped structure with the C atom bonded to the O atom, and the local minimum for the H-bonded arrangement OCO ... HOH. The global minimum was estimated to be 920 cm(-1) deep at the fourth order of MPPT combined with the extended spdf-quality basis set supplemented with bond functions. At the same level of theory the optimal H-bonded structure is 357 cm(-1) higher in energy, and reveals a small 10 degrees departure from the collinear arrangement OCO ... H-O. Both the T-shaped and H-bonded forms are primarily bound by the electrostatic term, which is twice as large as the dispersion component. One-dimensional sections of the potential-energy surface were subsequently used to calculate vibrational energy levels for the wagging motion of the water moiety in the T-shaped and H-bonded forms. Two-dimensional cuts of the PES along the intermolecular Jacobi coordinates, r and theta, were employed to simulate the dynamics of the stretch-bend coupling close to the minima. (C) 1998 American Institute of Physics. [S0021-9606(98)02033-9]. [References: 34]