We construct a rigid-body (5-dimensional) potential-energy surface for the water-hydrogen complex using scaled perturbation theory (SPT). An analytic fit of this surface is obtained, and using this, two minima are found: the global miniumum has C2v symmetry, with the hydrogen molecule action as a proton donor to the oxygen atom on water, where the OH bond and H2 are in a T-shaped configuration. The SPT global minimum is bound by 1097 muEh(Eh=4.359744 X 10-18 J). Our best estimate of the binding energy, from a complete basis set exrtapolation of coupled cluster calculations, is 107.1 muEh. The fitted surface is used to calculate the second cross virial coefficient over a wide temperature range (100-3000 K). Three complementary methods are used to quantify quantum statistical mechanical effects that become significant at low temperatures. We compare our results with experimental data, which are available over a moderate temperature range (230-700 K). Generally, good agreement is found, but the experimental data are subject to larger uncertainties.
Citation: Journal of Chemical Physics
Issue: No. 2
Pub Type: Journals
aqueous systems, hydrogen, intermolecular potential, second virial coefficient, water