Phase transition and mechanical properties of cesium bismuth silver halide double perovskites (Cs₂AgBiX₆, 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.