United-Atom Model for Molecules of the Type XHn

A united-atom model is used for the variational treatment of the systems HF, F—, O—, O— —, OH, OH—, H2O, and H3O+. This model utilizes one-electron wave functions which are centered on the single heavy nucleus in each system. The Hamiltonian is the correct one for the atoms in their true positions. Energies, equilibrium nuclear separations, and dissociation energies are calculated, as well as proton affinities of F—, O— —, O—, OH—, and H2O. The calculated values are in good agreement with experimental results.