“…The presence of heavy atoms in perovskite-based materials, such as Pb, demands the addition of spin-orbit coupling (SOC) effects for the valence and conduction states to obtain accurate electronic and optical properties. 38,39 In this study, we employed the second-variational approach, 40 incorporating an augmented number of electronic bands equivalent to twice the number of valence electrons. This adjustment is essential for enhancing the accuracy of the results.…”