The structural, elastic, electronic, optical, thermodynamic, and phonon properties of MgX2Se4 (X=Er, Ho, Tm, Y) spinel compounds

Abstract

In this study, the structural, mechanical, electronic, optical, thermodynamic, and phonon properties of MgX2Se4 (X = Er, Ho, Tm, Y) spinel compounds were systematically investigated using density functional theory (DFT). The electronic and optical properties were calculated employing the generalized gradient approximation within the Perdew-Burke-Ernzerhof (GGA-PBE) and the modified Becke-Johnson local density approximation (mBJLDA) exchange-correlation functionals. The optimized lattice parameters obtained from the structural optimization were found to be in good agreement with previously reported values. The calculated elastic constants satisfy the Born stability criteria, indicating that these compounds are mechanically stable. Electronic band structure analyses reveal that all MgX2Se4 compounds possess a direct band gap, confirming their semiconducting nature. Within the scope of optical properties, the real and imaginary parts of the dielectric function, along with other optical parameters, were computed and comprehensively analyzed. Thermodynamic analyses further reveal that the studied materials remain stable over a wide temperature range and exhibit behavior consistent with the Debye model. Overall, the phonon calculations confirm the dynamical stability of MgX2Se4 compounds, while the observed LO-TO splitting indicates significant long-range Coulomb interactions and polar lattice effects, highlighting their potential for optoelectronic applications.