In-depth analysis of ternary NaCuX (X = Se and Te) chalcogenides: Bridging structural elastic, electronic, and optical properties

Abstract

This study employs density functional theory (DFT) using the full potential linearized augmented plane wave plus local orbital (FP-LAPW+1o) approach to investigate the structural, elastic, electronic, and optical properties of NaCuX (X = Se and Te) compounds. Additionally, the modified Becke-Johanson (TB-mBJ) potential is applied to ensure accurate band gap results. Both compounds exhibit semiconducting behavior with a direct band gap at the Γ point. The computed elastic constants confirm mechanical stability for NaCuSe and NaCuTe, as evidenced by their respective bulk modulus, Young modulus, shear modulus, Poisson's ratio, B/G ratio, and elastic anisotropy. The materials display ductile characteristics, indicated by their B/G ratio and Poisson's ratio. The Debye temperature (θD) reveals that NaCuSe possesses the highest thermal conductivity. A decrease in θD is observed from NaCuSe to NaCuTe due to declining elastic constants. Additionally, anisotropy in acoustic velocities is assessed and discussed. The study's equilibrium structural properties align well with experimental data. Optical properties, including frequency-dependent dielectric function, refractive index, extinction coefficient, absorption coefficient, reflectivity, and energy loss function, are calculated and comprehensively analyzed.