Electronic structure and chemical bonding in oxygen conductors β-Bi4V2O11 and γ-Bi4V2O11

Ab initio calculations of the electron density are fulfilled for bismuth vanadate polymorphs: beta-Bi4V2O11 and gamma-Bi4V2O11. A semiconductor-type spectrum is obtained for both phases. The calculated bandgap value decreases in the direction from the beta to gamma phase. Chemical bond analysis shows an increase in the strength of covalent interactions in the series of Bi-V, Bi-O, and V-O bonds. The V-O bond strength in beta-Bi4V2O11 is appreciably higher than in the gamma phase. The relatively weak binding of oxygen in the tetragonal structure of gamma-Bi4V2O11 confirms the possibility of easier oxygen transport in the gamma phase than in the beta phase. The stability of the bismuth vanadate polymorphs and the oxygen-disorder features in the gamma-Bi4V2O11 structure are discussed using the results of calculation of the total energies of the phases. Bond overlap population analysis explains the existence of the homogeneous range and the feasibility of doping beta-Bi4V2O11 and gamma-Bi4V2O11. The possibility of using four-and five-charged d cations as stabilizers of the crystal structure of bismuth vanadates is discussed.