Anharmonic Stretching Frequencies of Local OH Bonds in Water Dimer: Ab Initio Potential Energy and Discrete Variable Representation

The fundamental and first overtone transition frequencies of local OH bonds of the hydrogen bond donor molecule in a water dimer were calculated by numerically solving one-dimensional Schrodinger equation with anharmonic potential energies obtained by ab initio quantum chemical methods at the near basis set limit. Among the various ab initio theories considered, the coupled cluster theory is found to give the most accurate frequencies in comparison with experiments, and the quadratic configuration interaction theory exhibits a similar accuracy. The calculated frequencies of the free and hydrogen-bonded OH bonds excellently agree with experimental frequencies of a gaseous dimer. It was found that the anharmonicity of the fundamental transition frequency is influenced by hydrogen bonding to a larger extent than the anharmonicity of the 1-2 transition frequency.