ELECTRONIC STRUCTURE OF CRYSTALS LiMO2 (M = B, Al, Ga, In, Tl)

10.25712/ASTU.1811-1416.2025.03.005

Abstract

Within the framework of density functional theory (DFT), the chalcopyrite structure of hypothetical LiMO₂ compounds (M = Al, Ga, In, Tl) was investigated for the first time, and equilibrium structural parameters were determined. Calculations of the energy band structure of LiMO₂ crystals were performed using CRYSTAL and Quantum Espresso software codes with LDA, GGA, PBE, and PBEsol functionals. The energy band structure and density of states of LiMO₂ crystals were calculated at high-symmetry points for chalcopyrites (T, Γ, N). All studied LiMO₂ crystals are wide-bandgap materials. The values of the bandgap Eg were estimated, and peculiarities of E_g variation and the total width of the valence band were established during cation substitution in the series B→Al→Ga→In→Tl. This affects the change in properties in the series of crystals from explicit dielectrics (the first three) to narrow-gap (LiTlO₂) semiconductors. Features of the conduction band edge formation were revealed depending on the chemical composition of LiMO₂ crystals. The conduction band minimum at the Γ point of LiMO₂ crystals has Γ_1C or Γ_3C symmetry, which results in the distinction between direct and pseudodirect bandgap crystals, respectively. It was revealed that the crystals exhibit properties of both semiconductors and dielectrics.