Structure and Acidity in Aqueous Solutions and Oxide-Water Interfaces

There have been a number of attempts to relate structural descriptors based on the bond-valence theory to the Bronsted acidity of (hydr)oxyacid monomers and oxide surface functional groups, via simple quantitative structure-activity relationships (QSARs). These models show some promise, but since they have been calibrated solely on monomers, it is difficult to know whether oxide surface functional groups are within their domain of applicability. In fact, there are strong reasons, including direct ab initio computation of equilibrium constants for surface functional groups, for doubting whether acidity QSARs based on the bond-valence theory are yet capable of accurately predicting acidity at the level of individual surface functional groups, despite some apparent successes. For progress to continue, we must further develop the relationship between bond valence and structural energy, so that we will be better able to construct widely applicable models