Electronic band structure and basic optical constants of TlGaSn2Se6, a promising NLO semiconductor: First-principles calculations under DFT framework

Abstract

We present results of band-structure computation under framework of density functional theory (DFT) of total and partial densities of states (DOS) of quaternary thallium gallium tin selenide, TlGaSn2Se6, a novel and promising material for application in non-linear optics. The present computation data are obtained employing different approaches for exchange-correlation (XC) potential to uncover the best fit of theoretical DOS curves to the experimental valence band (VB) spectrum of TlGaSn2Se6 compound as measured by X-ray photoelectron spectroscopy. Our findings show that the best fit of the theoretical and experimental data are detected in the case of application for XC potential of modified Becke-Johnson (MBJ) approach and involving in the computation procedure of the spin-orbit (SO) effect and the correction parameter U for highly correlated electrons of d symmetry. Based on our findings, we calculate band structure and primary optical constants of the quaternary thallium gallium tin selenide. The calculations indicate that this selenide is an indirect gap semiconductor in which the main input at the top und upper constituent of the TlGaSn2Se6 VB comes from Se 4p states, its central part is dominated by contributions of Sn 5p states. Further, Tl 6 s and Ga 4 s states are the most substantial contributors to the lower VB portion, while the VB bottom is prevailed by contributions of Sn 5 s states.