VIBRATIONAL DYNAMICS OF THE H2OHF COMPLEX - POTENTIAL-ENERGY AND ELECTRIC-DIPOLE MOMENT SURFACES

A total of 330 points on the potential energy and electric dipole mome nt surfaces of the ground electronic state of the H2O . HF complex hav e been calculated ab initio using the SCF method and many-body perturb ation theory (MBPT). To keep the calculations manageable, the geometry parameters of H2O were fixed at their experimental values and only ce rtain two-dimensional sections of the total surfaces have been evaluat ed. For each of the two-dimensional surface sections, analytic potenti al energy and electric dipole moment functions have been fitted throug h the points and corresponding vibration energy levels and effective e lectric dipole moments have been calculated using approximate vibratio nal Hamiltonians. The calculated values of resulting vibrational energ ies and effective electric dipoles form differently wide intervals for different vibrational modes. The intervals corresponding to the most interesting low frequency modes (out-of-plane and H2O vs HF stretching ) are very narrow and coincide satisfactorily with the corresponding e xperimental values. A very reasonable agreement has also been obtained for the equilibrium geometry, electric dipole moment and dissociation energy D(e), of the complex. These findings lead us to believe that t he calculated potential energy and electric dipole moment surfaces are sufficiently accurate for predicting purposes and rationalization of the so far unassigned spectral data of H2O . HF.