Relation between the Hydrated Electron Solvation Structure and Its Partial Molar Volume.

It is now generally accepted that the hydrated electron occupies a cavity in water, but the size of the cavity and the arrangements of the solvating water molecules have not been fully characterized. Here, we use the Kirkwood-Buff (KB) approach to examine how the partial molar volume () provides insight into these issues. The KB method relates to an integral of the electron-water radial distribution function, a key measure of the hydrated electron structure. We have applied it to three widely used pseudopotentials, and the results show that is a sensitive measure of the fidelity of hydrated electron descriptions. Thus, the measured places constraints on the hydrated electron structure that are important in developing and evaluating the model descriptions. Importantly, we find that does not reflect only the cavity size (and thus should not be used to infer the cavity radius) but is strongly dependent on the extended solvation structure.