Electronic, optical, and thermodynamic properties study of gadolinium chalcogenides (GdS, GdSe, GdTe) using density functional theory for optoelectronic applications

In this study, the electronic, optical, and thermodynamic properties of gadolinium chalcogenides (GdX: X = S, Se, and Te) were computed using first-principles methods with the Perdew–Burke–Ernzerhof (PBE) exchange–correlation functional, as implemented in the pseudopotential plane-wave approach. The results of the electronic properties of gadolinium chalcogenides confirm that they are low-bandgap-energy semiconductors. The energy bandgaps of GdS, GdSe, and GdTe were computed to be 2.4, 2.1, and 1.5 eV, respectively. The computation of reflectivity for gadolinium chalcogenides shows that they have minimum reflectivity in the visible region and maximum reflectivity in both the infrared and ultraviolet spectral regions. The direct bandgap energy of these compounds, the existence of imaginary dielectric function peaks in the visible region, and high reflectivity in the ultraviolet ranges of electromagnetic energy (photons) reveal the potential utilization of gadolinium chalcogenides in optoelectronic applications. Moreover, the temperature dependence of Helmholtz free energy, internal energy, entropy, and specific heat capacity at constant volume was analyzed to investigate the thermodynamic properties of gadolinium chalcogenides. The specific heat capacities for GdS, GdSe, and GdTe calculated at the Debye temperature (400 K) are 47.84, 49.16, and 49.67 J mol−1 K−1, respectively. The study confirmed the thermodynamic stability of gadolinium chalcogenides, highlighting their potential for various electronic applications.