Modeling of the influence of solvation on the vibrational spectra of high-symmetry molecular ions

An ab initio quantum-chemical method was used ro study the vibrational spec tra of Na3SbS4 in aqueous solutions. The Raman spectra of the corresponding anion were calculated based on a tetrahedral model. First, solvent effects were described with the use of the self-consistent reaction field model. A t the second stage, a method for explicitly taking into account the average electrostatic field of the ionic environment was introduced. The geometric configuration and the frequencies of vibrations not involving dipole momen t changes were insensitive to the parameters of the reaction field model. T he frequencies of Fz-type vibrations (d mu/dQ not equal 0) shifted to the r ed by values that correlated with the calculated IR band intensities. The i onic environment model allows a neutral system to be considered. Taking int o account the average field of counterions led to a decrease in internuclea r distances in the complex and increased all vibrational frequencies, which improved agreement with experiment.