Tuning the structural, electronic, magnetic, and optical properties of EuS via Nd²⁺ doping: a comprehensive study

This study employs first-principles density functional theory (DFT) calculations within the WIEN2K software framework to investigate the electronic, magnetic, and optical properties of EuS and Eu₀.₅Nd₀.₅S compounds. The computational methodology incorporates the Tran-Blaha modified Becke-Johnson (TB-mBJ) exchange-correlation potential to enhance the accuracy of electronic structure predictions. Structural parameters, including equilibrium lattice constants and unit cell volumes, were derived by fitting the total energy versus volume data to the Birch-Murnaghan equation of state (BME). The computed structural properties exhibit strong agreement with available experimental data, validating the reliability of the adopted computational approach. Electronic properties were examined via band structure (BS) calculations, supplemented by an in-depth analysis of the total and partial density of states (T-DOS and P-DOS). The band structure results confirm the metallic nature of both EuS and Eu₀.₅Nd₀.₅S, as indicated by the presence of conduction states at the Fermi level. Optical properties were systematically analyzed through key frequency-dependent response functions, including the real and imaginary components of the dielectric function [ε₁(ω) and ε₂(ω)], reflectivity spectrum [R(ω)], energy-loss function [L(ω)], refractive index [n(ω)], and absorption coefficient [α(ω)]. These optical parameters elucidate the interaction mechanisms between these materials and electromagnetic radiation, offering crucial insights into their potential applications in optoelectronic and photonic technologies.