Solvation effects on the vibrational modes in hydrated bicarbonate clusters

Abstract

HCO₃⁻(H₂O)_n clusters provide a model system to understand the solvation interaction between the bicarbonate ion and water. Based on harmonic analysis, ab initio molecular dynamics simulations, and comparison with infrared multiple photon dissociation spectra and with previous results on H₂PO₄⁻(H₂O)_n, the solvation effects on the vibrational modes of HCO₃⁻(H₂O)_n are analyzed. Hydrogen bond interactions have a significant impact on the vibration, especially when a hydrogen atom is directly involved in a particular mode. The COH bending mode is flattened, when the COH group is solvated by water molecules. The emergence of broad water libration modes indicates the aggregation of water molecules and the formation of a surface structure with bicarbonate on the surface.