Doctoral dissertation at Uppsala University 1993 for the degree of Doctor of Philosophy
The OH stretching vibrational spectrum is experimentally used as a measure of the strength of the hydrogen bond and other intermolecular interactions. Here the OH stretching vibration of the water molecule interacting with other water molecules and ions in clusters and crystals (LiClO4· 3H2O, LiOH·H2O, LiHCOO·H2O, ice II, VIII and IX) has been studied by ab initio methods The relative importance of the nearest-neighbour interactions and the long-range crystal field on the frequency and the electron density was identified. Relationships between the frequency and nearest-neighbour distances, O-H bond lengths and infrared absorption intensity were confirmed.
Molecular Dynamics simulations were used to calculate the OH stretching vibrational spectrum (frequencies and band width) in liquid water. The calculated spectrum was found to be highly sensitive to quantum-corrections and to the dynamics of the neighbouring molecules; both effects are necessary to include in theoretical calculations for the model to be realistic.
Periodic Hartree-Fock ab initio computations were performed for LiOH·H2O and ice VIII. In this method long-range environmental effects are taken properly into account. Electron densities, quadrupole coupling constants, uncoupled OH vibrations, Raman spectra, electronic band structure diagrams and strain-free structures were calculated. For ice VIII, an equation of state was derived and the changes in crystal geometry and vibrational properties brought about by the hydrostatic pressure in the range of 0 to 30 GPa were investigated.
Lars Ojamäe, Institute of Chemistry, Uppsala University, Box 531,
S-751 21 Uppsala, Sweden
(C) Lars Ojamäe 1993