Tight-Binding Model for Mixed Perovskites

We present a tight-binding description of mixed perovskites showing an application to Sn-Pb mixed systems. We discuss the parameterization procedure and the preliminary results obtained for $\text{MASn}_{0.5} ~\text{Pb}_{0.5} \mathrm{I}_{3}$. Our model shows a treatment of the band gap bowing observed for this perovskite alloy when Sn segregation is considered. Note that our method can be easily extended to include the description of all the perovskite crystal phases and more refined strain effects.