The influence of water interfacial potentials on ion hydration in bulk water and near interfaces

The surface potential at the water liquid–vapor interface is discussed in relation to experimental determinations of bulk absolute ion hydration free energies. 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 for the net potential are consistent with conclusions from previous classical simulations, suggesting a contribution from the net potential that can influence ion density profiles for single ions in water droplets.