An Ab Initio Study on the Elasticity and Optical Features of Semiconductor Lithium-Based Germanate Chalcogenides (li8ges6 and Li8gese6)

Abstract

This research presents the distinctive attributes of orthorhombic Li8GeCh6 (Ch = S and Se) compounds. The study delves into its structural and elastic properties, electronic behavior, and optical characteristics. Especially structural and mechanical features of the compounds have been analyzed by spin-effect computations, within Density Functional Theory (DFT), employing both local density approximation (LDA) and generalized gradient approximation (GGA). By optimizing the Wyckoff positions of atoms within its orthorhombic structure of crystal, it has been understood from Born's stability criteria and formation energies that both of the compounds are energetically synthesizable and structurally and mechanically stable. Additionally, first-principles calculations have been employed to examine the density of electronic states with the inclusion of orbitals and the electronic band structure for spin-up and spin-down states, revealing that compounds exhibit semiconductor character, with a direct band gap for both spin states. It is also seen that the band gap Eg is 2.10 eV for Li8GeS6 and 1.18 eV for Li8GeSe6 compound. Finally, complex dielectric functions as a function of frequency have been computed to assess its optical features, providing insights into both real and imaginary components of the dielectric function.