Dynamics of water molecules at liquid–vapour interfaces of aqueous ionic solutions: effects of ion concentration

The dynamical properties of water molecules at the liquid–vapour interfaces of aqueous NaCl solutions are studied by means of molecular dynamics simulations. The diffusion coefficients and the orientational relaxation times of the interfacial molecules of pure water and also the effects of ion concentration on these interfacial dynamical properties of aqueous solutions are investigated and the results are compared with those of the corresponding bulk phases. The inhomogeneous density, anisotropic orientational profiles and the surface tension are also calculated in order to characterize the location, width and the thermodynamic aspects of the interfaces and to explore their effects on the dynamical properties.