Ions at the liquid/vapor interface of methanol

We studied ions at the liquid/vapor interface of methanol using classical molecular dynamics techniques. Polarizable potential models were used to describe interactions among species. We characterized the transport mechanism of an iodide anion across the methanol interface. The computed potential of mean force showed a relatively small minimum well depth (i.e., -0.60 kcal/mol) located inside the Gibbs dividing surface. During the constrained mean force simulations, we found the iodide anion carrying some methanol molecules with it as it crossed the dividing interface. The computed density profiles of the salt NaI methanol interface indicated that the iodide anions were found nearer to the interface than the sodium cations, and no well-defined maxima were found for neither ion near the interface. By comparing this result with the corresponding result obtained from a simulation of the NaI saltwater interface, we can conclude that the probability of finding iodide anions at the liquid/vapor of water interface is significantly greater than at the methanol interface.