Effects of dispersion interaction on vibrational spectral diffusion in aqueous NaBr solutions: An ab initio molecular dynamics study

Abstract

Effects of dispersion interactions on the dynamics of water in bromide ion hydration shells have been studied by first principles simulations using a dispersion corrected density functional. The dynamics of vibrational spectral diffusion and its relations to hydrogen bond dynamics have been investigated for two different ion concentrations. It is found that the vibrational spectral diffusion of water molecules show faster dynamics with inclusion of dispersion interactions for both hydration shell and bulk water. The frequency calculations of hydration shell water reveal a weaker ion–water hydrogen bond than those between two water molecules. In the anionic hydration shell, the frequency of an OD bond is found to decrease with decrease of ion–water hydrogen bond distance. The hole dynamics calculations have been performed for further investigations of vibrational spectral diffusion of the two solutions. The current results are compared with those of recent experiments and other theoretical calculations.