Investigation of structural, electronic and optical properties of potassium and lithium based ternary Selenoindate: Using first principles approach

Highlights: • Our calculations reveal a direct band gap semiconductor nature for both materials. • The K and Li ions in two materials appear ionically bonded predominantly to crystal lattices with a covalency nature in In–Se pairs. • The calculated Eg (LiInSe₂)>Eg (KInSe₂) show an agreement with a decrease in bond energy for Se-p and In-s antibonding states. • The frequency dependent optical parameters are computed and discussed in detail which are consistent with other results. • An anisotropy is observed in the range (3.0–13.0) eV in the reflectivity spectra. Here we reported the first principle-based calculations for the structural and optoelectronic properties of AInSe₂ (A=K and Li) chalcopyrite type single crystals with-in the framework of density functional theory (DFT). The calculated structural parameters using the local density approximation (LDA) and general gradient approximation (GGA) are in a best agreement with existing experimentals and others theoretical results. The band structures and density of states of these materials are investigated and discussed in detail. Our calculations reveal a direct band-gap semiconductor type nature for both materials. The calculated band gaps follow that E_g (LiInSe₂)>E_g (KInSe₂) showing a good agreement for a decrease in bond energy for the corresponding In-s and Se-p anti-bonding orbital states. Furthermore, the frequency dependent linear optical properties, such as the complex dielectric functions, energy loss function, absorption coefficient, reflectivity, refractive index, the extinction coefficient and the real part of optical conductivity are also computed and discussed in detail. Our calculated optical results were found to be in a good agreement with the results from the literature There exists a significant variation in optical characteristics of both these materials. Our predicted calculated results would guide to understand the experimental and theoretical work on the basic material properties of these materials including crystal structures, optoelectronic properties, as well as their device applications.