Interpreting Vibrational Sum-Frequency Spectra of Sulfur Dioxide at the Air/Water Interface: A Comprehensive Molecular Dynamics Study

We investigated the solvation and spectroscopic properties of SO2 at the air/water interface using molecular simulation. Molecular interactions from both Kohn-Sham (KS) density functional theory (DFT) and classical polarizable models were used to understand the properties of SO2:(H2O)(x) complexes in the vicinity of the air/water interface. The KS-DFT was included to allow comparisons with vibrational sum-frequency spectroscopy through the identification of surface SO2:(H2O)(x) complexes. Using our simulation results, we were able to develop a much more detailed picture of the surface structure of SO2 consistent with spectroscopic data obtained by Richmond and co-workers (J. Am. Chem. Soc. 2005, 127, 16806). We also found many similarities and differences between the two interaction potentials, including a noticeable weakness of the classical potential model in reproducing the asymmetric hydrogen bonding of water with SO2 due to its inability to account for SO2 resonance structures.