PNNL

Abstract

Although there is a consensus that large, polarizable anions will adsorb to the air-water interface, the precise interactions that give rise to surface enhancement are still being debated. Previously, we have demonstrated that there is a significant dependence on the choice of molecular interaction potential for iodide adsorption at the air-water interface. Specifically, density functional theory (DFT) based interaction potentials lead to significantly less adsorption than empirical interaction potentials that include polarization. We have also demonstrated that DFT based interaction potentials can accurately capture the structure of the first solvation shell of both simple and polyatomic anions as compared to multi-edge X-ray absorption fine structure (XAFS) experiments. We continue to push DFT by examining the surface propensity and structure of polyatomic anions that exhibit both chaotropic and kosmotropic characteristics as classified by the Hofmeister series. We will investigate the role of local solvation effects of SCN- and compare to previous studies on I- and IO3- under both bulk and interfacial conditions. A picture emerges where we can correlate local solvation stucture to the Hofmeister series.