THEORY OF HYDROGEN BOND - ELECTRONIC STRUCTURE AND PROPERTIES OF WATER DIMER

High-accuracy molecular-orbital calculations using essentially Hartree-Fock quality atomic orbitals as a basis have been carried out on different geometries of the water dimer. Different basis sets have been considered. The molecular-orbital approach is shown to well represent the geometry and heat of formation (-5.3 kcal/mole) of the water dimer as well as general infrared spectral properties of the hydrogen bond. The individual molecular-orbital energies are shown to increase for the electron acceptor and to decrease for the electron donor. This trend in energies is proposed as a quantitative organizing principle for not only H-bond formation but all donor-acceptor interactions.