WATER-MOLECULES IN DIFFERENT CRYSTAL SURROUNDINGS - VIBRATIONAL O-H FREQUENCIES FROM ABINITIO CALCULATIONS
1992 (English)In: Journal of Chemical Physics, ISSN 0021-9606, E-ISSN 1089-7690, Vol. 96, no 12, 9035-9045 p.Article in journal (Refereed) Published
Ab initio quantum-mechanical calculations of anharmonic frequencies for the water O-H vibrations have been performed for a series of crystalline hydrates. In each case, the potential-energy curve for the uncoupled water O-H stretch was derived at the Moller-Plesset MP2 level. Nearest neighbors of the water molecule were explicitly included in the supermolecule and the rest of the surroundings were mimicked by point charges to reproduce the crystal field out to infinity. The time-independent Schrodinger equation for the motion of the proton in this potential well was solved variationally and the frequency was obtained from the energy difference between the 0 and 1 eigenstates. Computed frequencies can be directly compared with existing infrared data for isotope-isolated water molecules in these hydrates. The compounds selected (LiClO4.3H2O, LiHCOO.H2O, LiOH.H2O) exhibit experimental O-H frequency shifts in a wide range, from - 150 down to - 930 cm-1. Good agreement is found between experimental and theoretical frequencies (experimental values in parentheses): 3596 (3556) for LiClO4.3H2O, 3129 (3112) and 3488 (3390) for LiHCOO.H2O, and 2817 (2775) cm-1 for LiOH.H2O. Correlation curves of typical H-bond parameters such as nu(O-H) vs R(H...O), r(e)(O-H) and nu(OH)/nu(OD) have been computed and compared with experiment. The vibrational intensities are also discussed.
Place, publisher, year, edition, pages
1992. Vol. 96, no 12, 9035-9045 p.
IdentifiersURN: urn:nbn:se:liu:diva-115176ISI: A1992HZ09800042OAI: oai:DiVA.org:liu-115176DiVA: diva2:794194