title: Structural, Electronic, and Optical Properties of BiOX1-xYx (X, Y = F, Cl, Br, and I) Solid Solutions from DFT Calculations.
abstract: Six BiOX1-xYx (X, Y = F, Cl, Br, and I) solid solutions have been systematically investigated by density functional theory calculations. BiOCl1-xBrx, BiOBr1-xIx, and BiOCl1-xIx solid solutions have very small bowing parameters; as such, some of their properties increase almost linearly with increasing x. For BiOF1-xYx solid solutions, the bowing parameters are very large and it is extremely difficult to fit the related calculated data by a single equation. Consequently, BiOX1-xYx (X, Y = Cl, Br, and I) solid solutions are highly miscible, while BiOF1-xYx (Y = Cl, Br, and I) solid solutions are partially miscible. In other words, BiOF1-xYx solid solutions have miscibility gaps or high miscibility temperature, resulting in phase separation and F/Y inhomogeneity. Comparison and analysis of the calculated results and the related physical-chemical properties with different halogen compositions indicates that the parameters of BiOX1-xYx solid solutions are determined by the differences of the physical-chemical properties of the two halogen compositions. In this way, the large deviation of some BiOX1-xYx solid solutions from Vegard's law observed in experiments can be explained. Moreover, the composition ratio of BiOX1-xYx solid solutions can be measured or monitored using optical measurements.
authors.affiliation: Faculty of Materials Science and Engineering, Kunming University of Science and Technology, Kunming 650093, People's Republic of China.|Yunnan Key Laboratory of Micro/Nano Materials &Technology, School of Materials Science and Engineering, Yunnan University, Kunming 650504, People's Republic of China.
authors.forename: Zong-Yan
authors.initials: ZY
authors.lastname: Zhao
authors.affiliation: Key Laboratory of Nanodevices and Applications, Suzhou Institute of Nano-Tech and Nano-Bionics, Chinese Academy of Sciences, Suzhou 215123, People's Republic of China.
authors.forename: Qing-Lu
authors.initials: QL
authors.lastname: Liu
authors.affiliation: Faculty of Materials Science and Engineering, Kunming University of Science and Technology, Kunming 650093, People's Republic of China.
authors.forename: Wen-Wu
authors.initials: WW
authors.lastname: Dai