The influence of water interfacial potentials on ion hydration free energies and density profiles near the surface

TL;DR

This paper examines how water's interfacial electrostatic potential influences ion hydration free energies and ion density profiles near the water surface, highlighting the importance of the net electrostatic potential at uncharged solutes.

Contribution

It clarifies the role of the net electrostatic potential at uncharged solutes in relating hydration free energy differences and surface potential estimates, integrating classical and quantum insights.

Findings

Quantum results support increased anion density at the surface.

The net electrostatic potential explains differences in hydration free energy tabulations.

Classical and quantum methods are consistent in their conclusions.

Abstract

The surface or contact potential at the water liquid-vapor interface is discussed in relation to determinations of absolute ion hydration free energies and distributions of ions near the interface. It is shown that, rather than the surface potential itself, the net electrostatic potential at the center of an uncharged solute can aid both in relating differences between tabulations of hydration free energies and in explaining differing classical and quantum surface potential estimates. Quantum mechanical results are consistent with conclusions from classical simulations that there is a net driving force that enhances anion density at the surface relative to cations.