Phase transition and mechanical properties of cesium bismuth silver halide double perovskites (Cs 2 AgBiX 6 , X = Cl, Br, I): a DFT approach.

Double perovskite-based silver and bismuth Cs2AgBiX6 (X = Cl, Br, I) have shown a bright future for the development of low-risk photovoltaic devices due to their high stability and non-toxicity of their elements, unlike Pb-based perovskites. Despite the great focus on the optoelectronic properties of Cs2AgBiX6 double perovskites, there are limited studies on the behavior of their structural properties. Herein, we carefully examined the cubic structure of Cs2AgBiX6 double perovskites, identifying a pseudo-cubic (ps-cubic) phase, which is similar to the initial cubic phase. The observed pseudo-cubic phase is more consistent with previous experimental results demonstrating higher elastic properties, which are useful for designing optoelectronic devices.