Solvation energy and vibrational spectrum of sulfate in water – An ab initio quantum mechanical simulation

The normal modes of tetrahedral (Td) sulfate ion as well as the librational and vibrational motions of water molecules in the first hydration shell of sulfate ion and in the bulk phase were evaluated by means of velocity autocorrelation functions (VACFs) obtained by an ab initio quantum mechanical charge field (QMCF) molecular dynamics (MD) simulation and subsequent normal coordinate analyses. The calculated frequencies reflect the influence of water molecules in the first hydration sphere on the structure of sulfate ion. The calculated hydration energy of −249 ± 17 kcal mol−1 agrees well with the average experimental value of −245 kcal mol−1.