Ab initio molecular orbital calculations of the infrared spectra of hydrogen-bonded complexes of water, ammonia and hydroxylamine. Part 11. The atomic polar tensors, and their invariants, of the monomers and the binary hydrogen-bonded complexes

Abstract

The atomic polar tensors of the monomers, homodimers and 1:1 binary complexes of water, ammonia and hydroxylamine are reported. These quantities are used to derive the three invariants of each atom in each species, namely the effective charge, the mean dipole derivative and the anisotropy. The trends in the values of these invariants are discussed in relation to the type and strength of hydrogen bond found in each associated species. The invariants, in turn, are used to obtain values for the undeformability parameters and the mass-weighted squared effective charges, and the trends in these quantities are discussed. The results are used in an interpretation of the predicted intensity changes in the infrared spectra of the dimers and complexes, relative to the monomers, reported in a recent series of publications. The intensity changes are also related to the variations of the calculated Mulliken charges of the bonded hydrogen atoms in each hydrogen-bonded environment.