Ions at hydrophobic aqueous interfaces: Molecular dynamics with effective polarization

The affinity of halide anions to the water/oil interface is investigated using molecular dynamics simulations effectively accounting for polarization effects by an electronic continuum correction, which is practically realized via rescaling of the ionic charges. This simple and computationally efficient correction to nonpolarizable simulations is suited for electronically homogeneous media, and we show that it works well also for the water/oil interface, which exhibits practically no electronic discontinuity. Consequently, for this interface, the current simulations give interfacial affinities of halide anions, which are consistent with experiment and previous explicitly polarizable calculations. For the water/vapor interface, however, the present method overestimates the anionic surface affinities, which can be traced back to the abrupt change in the electronic part of the relative permittivity upon moving from the liquid to the gas phase.