First-Principles Calculation Of Temperature-Dependent Electronic Transitions Mechanism In V Or Nb Substituted Bifeo3

Here, we present a simulation study of temperature-dependent electronic transitions in BiVO3 (BVO) and BiNbO3 (BNO) using density functional theory (DFT) together with generalized gradient approximation (GGA) and two-dimensional correlation analysis (2D-CA). The results indicate that heat accumulation can accelerate the degeneracy of V-3d orbital in BVO and the splitting of Nb-4d orbital in BNO at 750 K. We found changes in the type of d-p hybrid orbital as follows, for BVO: V-d(x)(+y)(2)(2) + d(Z)(2)-O-2p(z) -> V-d(x)(+y)(2)(2)-O-2p(z); and for BNO: Nb-d(x)(+y)(2)(2)-O-2p(z) -> Nb-d(x)(+y)(2)(2) + d(Z)(2)-O-2p(z). Furthermore, we found changes in the type of hybrid orbital leading to the following electron-electron interactions, for BVO: t(2g) (V-d(Z)(2)-O-2p(z)) + e(g) (V-d(x)(+y)(2)(2)-O-2p(z)) -> t(2g) (V-d(x)(+y)(2)(2)-O-2p(z)); and for BNO: t(2g) + e(g) (Nb-d(x)(+y)(2)(2) + d(Z)(2)-O-2p(z)) -> t(2g) (Nb-d(x)(+y)(2)(2)-O-2p(z)) + e(g) (Nb-d(z)(2)-O-2p(z)). The electronic transitions are determined by a charge-transfer from the occupied O-2p(4) orbitals to the unoccupied V-3d(3) (or Nb-4d(3)) and Bi-6p(3) orbitals. Due to the temperature-dependent electronic structure closely related to these electronic transitions, this study provides a new perspective for the design and improvement of BFO-based temperature-sensitive devices.