First-principles computation of the electronic structure and optical properties of Tl3PbBr5 and TlPb2Br5: Application of the TB-mBJ+U+SOC technique

Abstract

Results of computation of the electronic structure of low-temperature (LT) orthorhombic (space group P212121) and high-temperature (HT) tetragonal (space group P41) polymorphous forms of Tl3PbBr5 as well as of TlPb2Br5 (monoclinic space group P21/c) compound as compared to the experimental XPS studies of these bromides are presented. Our results indicate that the best correspondence of the theoretical total density of states and the experimental XPS valence-band spectrum is detected when the computations are carried out employing the augmented plane wave + local orbitals method within a Density Functional Theory (DFT) formalism and using the modified Becke-Johnson (mBJ) functional as refined by Tran-Blaha and considering also the Hubbard correction parameter U for strongly correlated d electrons associated with Tl and Pb atoms and spin-orbit coupling (SOC) effect (TB-mBJ + U + SOC technique). Based on these findings, using the mBJ + U + SOC technique, we study in detail partial densities of states of LT- and HT-modifications of Tl3PbBr5 and of TlPb2Br5. Furthermore, for the above ternary bromides, for the first time, the main optical properties were calculated.