Hydrogen bonding from a valence bond theory perspective: the role of covalency.

A valence bond theory based method has been developed to decompose hydrogen bond energies into contributions from geometry, electrostatics, polarization and charge transfer. This decomposition method has been carried out for F-HFH, F-HOH2, F-HNH3, HO-HOH2, HO-HNH3, and H2N-HNH3. Localized valence bond self-consistent field (L-VBSCF) and localized breathing orbital valence bond (L-BOVB) calculations were performed at the PBEPBE/aug-cc-pVDZ optimized geometries.