“XA6” octahedra influencing the arrangement of anionic groups and optical properties in inverse-perovskite [B6O10]XA3 (X = Cl, Br; A = alkali metal)

Abstract

Exploring the effect of microscopic units, which set up the perovsikte framework, is of importance for material design. In this study, a series of borate halides with inverse-perovskite structures [B₆O₁₀]XA₃ (X = Cl, Br; A = alkali metal) have been studied. It was revealed that the distortion and volume of XA₆ octahedra influence the arrangement of anionic groups, which leads to the flexibility of the perovskite-related framework and differences in optical properties. Under the structural control scheme, the structure of Rb₃B₆O₁₀Cl was predicted. The stability of the predicted structure was confirmed by an ab initio density functional theory-based method. The calculation shows Rb₃B₆O₁₀Cl has a short UV cutoff edge of less than 200 nm, a moderate birefringence and a large second harmonic generation response.