Communication: Molecular dynamics simulations of the interfacial structure of alkali metal fluoride solutions

Molecular dynamics simulations are carried out to study the interfacial profiles of alkali metal fluoride solutions (NaF, KF, RbF, and CsF) at 1 atm and 300 K. For these solutions, we find that the occupancy of the cations in the interfacial region is comparable to or greater than that of the F- anion. Cations that have weaker hydration abilities have higher concentrations at the interface. The order of enhanced concentrations of cations at the interface is Na⁺ < K⁺ < Rb⁺ < Cs⁺. The partitioning mechanism can be understood in terms of ionic hydration theory, which shows that the interfacial behavior of ions is related to hydration interactions. This work provides new insight into the interfacial structure of electrolyte solutions and enriches the theory of electrolyte interfaces.