Computational studies of aqueous interfaces of RbBr salt solutions.

We computed the structure factor and the corresponding x-ray reflectivity of an aqueous interface of RbBr salt solution and used molecular dynamics techniques to compare polarizable and nonpolarizable potential models for molecular interaction. Our computed electron and number density profiles clearly demonstrate that the polarizable Br(-) anions are enhanced at the water/vapor surface while the nonpolarizable Br(-) anions are depleted from it. The observation of Br(-) ions at the interface contradicts a recent interpretation that was based on experimentally measured x-ray reflectivity data.