Ab initio calculation of the vibrational force field of the water dimer

Abstract

The geometry and vibrational frequencies of the water dimer are calculated using ab initio LCAO-SCF theory. Most of the results were obtained using a split valence basis set. Some calculations with a larger basis set having polarization functions are also reported. The findings are somewhat dependent on the basis set with the split valence basis set giving too strong a hydrogen bond and consequently force constants which are too large. The intramolecular frequency shifts are in reasonable agreement with experimental results. The low frequency intermolecular vibrations are also determined and are qualitatively consistent with the infrared spectrum of liquid water.