FP-LAPW calculations of structural, electronic, and optical properties of alkali metal tellurides: M₂Te [M: Li, Na, K and Rb]

Structural, electronic, and optical properties of alkali metal tellurides M₂Te [M: Li, Na, K, and Rb] are investigated in the framework of density functional theory within generalized gradient approximation. The calculated structural parameters are in excellent agreement with the experimental data. The electronic band structure calculations show that tellurides of Li, K, and Rb have an indirect fundamental energy band gap, whereas Na₂Te has a direct fundamental energy band gap. To explicate the contribution of anion and cation states to the electronic band structure, the electronic density of states for these compounds has been analyzed. Optical properties such as complex dielectric function, absorption coefficient, refractive index, extinction coefficient, and reflectivity are reported for a wide range of photon energy and are discussed on the basis of corresponding electronic band structure. Furthermore, the electron energy-loss functions for M₂Te compounds are also predicted. In order to validate the performance of the ab initio calculation reported herein, we systematically study the electronic and optical properties of wide band gap M₂Te compounds and compare them with available theoretical and experimental data of M₂O, M₂S, and M₂Se compounds.