Reconciliation of valency ambiguity in V₂TiO₅ using XANES spectroscopy

The structure of V₂TiO₅ involves a distribution of the two metal species between two crystallographic sites. The sites between the shear planes are occupied solely by vanadium as V^III, while the shear-plane sites are occupied by both metal atom species, vanadium and titanium. An analysis of the metal-oxygen distances could not distinguish between the two reasonable alternatives for the valency distribution, viz V^III/Ti^IV or V^IV/Ti^III. By examining the XANES spectra of the title compound at both vanadium and titanium K edges the valency distribution can be confidently assigned as V^III/Ti^IV. The usefulness of XANES spectroscopy for solving similar problems involving valency ambiguity is evident.