The Electronic Band Structure of the BaSnO3 and SrSnO3 Perovskites Calculated within the GGA and GW Approaches.

The Green’s function method, implemented in the first order of the perturbation theory (GW), was applied for an accurate description of the electronic structure of cubic BaSnO₃ and SrSnO₃ perovskites. First, the band structure of these materials was calculated within the generalized gradient approximation (GGA). Then, in order to obtain the accurate band gaps, the quasiparticle corrections to the eigenenergies were evaluated. The calculated electronic structure by means of the GW approximation was compared to the structure obtained within the GGA. The application of quasiparticle corrections to the eigenenergies led to a significant widening of the band gaps and provided a much better agreement with the experimental data. The GW corrections to the band energies, found for both crystals at the points of the first Brillouin zone, are quite different. Consequently, the use of a scissor operator can lead to errors in a calculation of the optical constants. [ABSTRACT FROM AUTHOR]