Electronic and optical characteristics of CaLiX3 (X = Cl, Br, I) perovskite compounds using the Tran-Blaha modified Becke-Johnson potential

We present the results of a comprehensive investigation using the full-potential linearized augmented plane wave approach to analyze the structural characteristics, electronic structures, and optical spectra of the perovskite compounds CaLiX3 (X = Cl, Br, or I). Various functionals were employed to simulate the exchange-correlation interactions. The calculated equilibrium structural parameters, obtained using the generalized gradient approximation, are consistent with the existing findings in the literature. The computed electronic structures reveal that the Tran-Blaha modified Becke-Johnson potential significantly enhances the bandgap. For all CaLiX3 compounds studied, we predicted an indirect bandgap. Additionally, we observed a gradual decrease in the bandgap as the atomic size of the X element increases. The electronic states constituting the various energy bands were evaluated by computing the partial and total densities of states. In addition, we computed a variety of optical spectra, including the complex dielectric function, absorption coefficient, refractive index, extinction coefficient, reflectivity, and electron energy loss function. The results demonstrate that a decrease in the bandgap leads to an increase in the zero-frequency limit of the dielectric function epsilon(0). The origins of the peaks and structures in the optical spectra were identified.