IR spectra of phosphate ions in aqueous solution: predictions of a DFT/MM approach compared with observations

The phosphate ions HPO4(super 2-) and H2PO4(super -1) are analyzed since sizable solvation effects are expected for the IR spectra of these strongly polarizable ions. The widths, intensities, and spectral positions of the resultant bands are compared with experimental IR spectra for the purpose of checking the computational procedures, which provide insights into the merits and limitations of the available density functional theory (DFT)/molecular mechanisms (MM) approach to the prediction of IR spectra in the condensed phase.