Ion clustering in aqueous salt solutions near the liquid/vapor interface

Abstract

Molecular dynamics simulations of aqueous NaCl, KCl, NaI, and KI solutions are used to study the effects of salts on the properties of the liquid/vapor interface. The simulations use the models which include both charge transfer and polarization effects. Pairing and the formation of larger ion clusters occurs both in the bulk and surface region, with a decreased tendency to form larger clusters near the interface. An analysis of the roughness of the surface reveals that the chloride salts, which have less tendency to be near the surface, have a roughness that is less than pure water, while the iodide salts, which have a greater surface affinity, have a larger roughness. This suggests that ions away from the surface and ions near the surface affect the interface in opposite ways.

Chemical equilibria of aqueous ammonium–carboxylate systems in aqueous bulk, close to and at the water–air interface

“…76 The former has been shown in several studies of the halide ions in water with iodide coming closest to the water-air interface. [77][78][79][80] At the same time neutral species preferring non-polar solvents are in fact promoted to be at the water-air interface or very close to it.…”

Plasma physics of liquids—A focused review

“…279 On the atomic scale, a liquid surface is not planar, but characterized by thermally activated capillary waves, 280 as well as perturbations induced by adsorbed surface-active solute ions. [281][282][283] As stated by a simulation study in Ref. 284, the molecular orientation in the interface layer depends on local surface fluctuations, since dipoles point towards the gas phase on extrusions and lie flat on the surface elsewhere.…”

Surface Potential of the Air/Water Interface

“…Furthermore, the water surface has its own roughness, that would increase the surface area by approximate 15 , and form nanoscopic surface waves capillary waves 56 . In order to exclude the effect of capillary waves on the distribution of species within the interface, a new intrinsic method, call identification of truly interfacial molecules was proposed and successfully applied 25, 57 60 .…”