An Ab-initio Investigation of LiBeX (X = Sb, Bi) Semiconductors For Opto-electronic Applications

Half Heusler compounds possess a broad array of characteristics which make them well suited materials for diverse functional applications. The extant study intended to scrutinize the structural, phononic, opto-electronic, elasto-mechanical and pressure induced properties of LiBeX (X = Sb, Bi) compounds. This investigation employed DFT based WIEN2k and VASP simulation packages by considering PBE-GGA, WC and TB-mBJ exchange correlation schemes to better corroborate the outcomes. The investigated compounds have successfully passed the energetic, lattice dynamic and mechanical stabilities. Electronic structure calculations with TB-mBJ functional revealed indirect band gaps of 1.007 and 0.789 eV for LiBeSb and LiBeBi compounds respectively. The partial charge density distribution in HOMO and LUMO disclosed maximum localization of charge around X-site atoms. The examination of COHP revealed the strongest Be-X bonding interactions among the bonding pairs. The physio-mechanical features indicated the brittle and mechanical anisotropic behavior of both compounds with covalent bonding characteristics. The compounds found active in the visible and lower ultraviolet spectrum regarding opto-electronic applications. The determined properties align well with prior theoretical findings. The comparative analysis suggests that the mBJ approach is highly recommended for treating the band gap of semi-conducting materials.