Predicting points of zero charge of oxides and hydroxides

Pauling's electrostatic valence principle has been applied to describe the surface-charging mechanism of oxides in an aqueous environment. This approach has led to the development of an equation with which one can predict the points of zero charge (PZC) of oxides and hydroxides from crystallographic data. The equation proposed in the present work is an improved version of Parks' PZC equation. The improvements are the following: (i) The equation does not incorporate correction terms to take the cation coordination numbers into account; (ii) the PZC of a complex oxide can be predicted directly from crystallographic data instead of from “assumed” PZCs of its component oxides; and (iii) one can use the mean metal-oxygen bond distance of a crystal instead of the ionic radii tabulated by Parks, which are not consistent with the up-to-date values.