Electronic properties and crystal structures of double-perovskites, Ba2BiIIIBiVO6,Ba2PrBiO6, and Ba2PrSbO6: First-principles study

Abstract

In recent experiments, a significant band gap widening was observed when Sb was substituted for Bi in the double-perovskite Ba2PrBiO6. In this work, we study a series of double-perovskites, Ba2BiIIIBiVO6, Ba2PrBiO6, and Ba2PrSbO6 using the first-principles density functional theory with the Heyd-Scuseria-Ernzerhof hybrid functional to investigate the substitution effect on the structural and electronic properties. We find that the two topmost valence bands are disappeared on the substitution of PrIII for BiIII, and the two bottommost conduction bands are disappeared on the substitution of SbV for BiV, causing the significant band gap widening. Further, our calculation suggests that the Ba2PrPrBiO6 is a possible candidate as a source of the PrIV signal observed in the experiment. We find that the B-site disordering atomic configuration, Ba2B″VB′IIIO6, are restored to those of the original structures. On the other hand, our results also suggest the importance of the partial B-site disorder to explain the experimentally observed band gaps.