First-principles investigation of SrXSe2 (X = Fe, Co, Ni) compounds: A comparative study of structural, electronic, optical, and thermoelectric properties

This study presents a detailed first-principles investigation into the structural, electronic, optical, and thermoelectric properties of SrXSe₂ (X = Fe, Co, Ni) compounds, utilizing density functional theory (DFT) within the WIEN2k computational framework. The substitution of barium (Ba) with strontium (Sr) is strategically explored to retain or enhance the favorable half-metallic and semiconducting properties observed in Ba-based counterparts.

Structural optimization confirms thermodynamically stable monoclinic phases, characterized by negative formation energies and positive decomposition energies, thereby validating the intrinsic stability of these materials. Spin-polarized electronic band structure calculations reveal robust half-metallicity, with a direct bandgap in the spin-up channel and metallic conductivity in the spin-down channel. Density of states (DOS) analyses highlight strong hybridization between transition metal d-orbitals and selenium p-orbitals, which plays a critical role in shaping the electronic structure.

Optical analyses exhibit pronounced peaks in the dielectric function and refractive index across the visible spectrum, reinforcing the suitability of these materials for integration into optoelectronic and photonic devices. From a thermoelectric standpoint, the SrXSe₂ compounds display high Seebeck coefficients, low thermal conductivity, and competitive figures of merit (ZT), indicating their strong potential for efficient thermoelectric energy conversion.

Collectively, the results demonstrate that SrXSe₂ materials not only preserve the multifunctional advantages of their Ba-based analogs but also emerge as compelling candidates for future applications in spintronics and sustainable energy technologies.