Ions at the air/water interface

We present results from theoretical studies of aqueous ionic solvation of alkali halides aimed at developing a microscopic description of structure and dynamics at the interface between air and salt solutions. The traditional view has depicted the air/solution interface of simple electrolytes as being devoid of ions. However, it is now firmly established that polarizable anions, such as the heavier halides, occupy the surface of small to medium sized water clusters. Using a combination of theoretical calculations, including ab initio quantum chemistry, Car-Parrinello molecular dynamics simulations, and primarily molecular dynamics simulations based on polarizable force fields, we present a unified view of the interfacial structure of aqueous ionic clusters and bulk solutions. Indeed, we demonstrate that the heavier halogen anions have a propensity for the interface that is proportional to their polarizabil∗Electronic mail: [email protected] †Electronic mail: [email protected]