From Geometry to Electronic Structure: Understanding Halide Perovskite Alloys through Local Motifs

Understanding how complex thermodynamic and electronic properties of real solids emerge from simple geometric motifs has been a long-standing goal in materials science. Here, we reveal that the intricate landscape of density functional theory (DFT)-calculated properties in halide perovskite alloys can be effectively captured by local geometric descriptors. Using the multi components alloys in different atomic sites (A, B and X), we show that the mixing enthalpy—a key measure of alloy stability—correlates linearly with a purely geometrical quantity: the excess B–X–B′ bond-angle, which reflects octahedral tilting within polymorphous structures. This correspondence establishes a direct link between thermodynamic stability and geometry. We further demonstrate that the band gap of these alloys follows the average B–X bond length, revealing a second, independent geometric correlation. Together, these findings introduce a framework in which fundamental quantum-mechanical properties can be rationalized through intuitive, local-geometry descriptors. This approach provides a pathway for understanding and predicting the stability and electronic behavior of multicomponent halide perovskite alloys.