Understanding the factors that contribute to ion interfacial behavior

Factors that affect ion behavior at the air–water interface from computer simulations are reviewed, specifically addressing those that influence ion induced dipoles, and the effect of charge delocalization. These are discussed in relation to how the molecular model influences them, such as how electrostatic damping influences the anion induced dipole, and how utilizing a multi-state model for hydronium and hydroxide ions influence their interfacial behavior by delocalizing their charges. Furthermore, the influence of ion pairing on interfacial behavior is discussed, focusing on how the presence of a cation influences halide and hydroxide ion interfacial free energies. For halides, a cation enhances its induced dipole and lowers its interfacial free energy, while for hydroxide, the presence of a cation reduces its propensity for the air–water interface.