Chemical and Structural Trends on Stability and Electronic Properties of CsMX₃ (M = Ge, Sn, or Pb; X = F, Cl, Br, or I) Inorganic Perovskite Polymorphs Including Relativistic and Quasiparticle Effects

High Resolution Image Download MS PowerPoint Slide Inorganic perovskites are complex compounds currently associated with photovoltaic and optoelectronic technology but at the same time with great experimental and theoretical challenges. The potential of this class of materials is immense, as, in addition to chemical diversity, there exists a set of energetically competitive crystal structures. In this work, we present a systematic study of polymorphism by calculating 84 inorganic perovskites (12 compounds in 7 crystal structures) using a rigorous theoretical model that includes quasiparticle corrections via DFT-1/2, coupled with relativistic effects. This approach provides a broader and more reliable overview of the properties of these materials. We establish how chemical and structural trends govern stability, shape internal structures, and modulate the band gap, based on the correlations obtained between these quantities. The main observed trend for increasing band gap follows the structural sequence: cubic → tetragonal → γ- Pnma → rhombohedral → δ- Pnma . Individual band gap values are generally in excellent agreement with the full range of available theoretical and experimental data, with the exception of experimental values for cubic structures, for which the underestimation is quantified and discussed. Moreover, we provide reliable predictions for potentially interesting yet underexplored systems. These results reinforce the feasibility of structural band gap engineering in these compounds and outline viable pathways for its implementation to tune optoelectronic properties through the combined control of elements and structure.