Structure And Chemical Bond Of Perovskite Crystal

From the viewpoint of chemical bond of perovskite crystal, the structural stability and formability of perovskite crystal were carefully investigated. The governing factors of structural formability and stability of perovskite can be obtained from the experimental data, and then are used to predict novel compounds with perovskite structure.We show that polyhedral volumes can be used to quantitatively identify A-O and B-O equilibrium bond lengths. With the use of equilibrium bond lengths, the observed tolerance factor of ABO3-type perovskite oxides were investigated in 240 ABO3-type perovskite structures. Analysis of the available data indicates that the observed tolerance factor is superior to the tilt angle for quantitatively identify the distortion of perovskite structure.The most distorted structure belongs to Pbnm space group, and the critical value of observed tolerance factor for common structural phase transitions Pbnm(?)R3c and Pbnm(?)I4/mcm is about 0.986.With the use of polyhedral factor, tolerance factor derived from the ideal bond lengths and the bond characteristic, the structural formability of ABX3-type perovskite oxides and were quantitatively investigated in all possible ABX3-type compounds including perovskite oxides and halides. The result indicates that 1191 compounds may form perovskite structure in 4124 possible ABX3-type compounds, which can be the initial set of candidate structure assumed. The structural formability and transition characteristic of perovskites with 6 different tilt systems were also studied. The predicted crystal structure is performed by distorting the structure to make bond valence sum of A ions equal to its ideal valence state.