A first principles analysis of pressure effects on the physical and optical properties of the FeSe chalcogenide superconductor

This work investigates the structural, electronic, optical, and mechanical properties of FeSe using advanced density functional theory (DFT). Understanding the high-pressure physical behavior of iron selenide superconductors is crucial for elucidating their superconducting mechanisms. In this study, first-principles DFT calculations are employed to examine the influence of pressure on the structural, mechanical, electronic, and superconducting properties, along with the Debye and melting temperatures of tetragonal FeSe. The mechanical analysis indicates that FeSe remains mechanically stable up to 7 GPa. Hydrostatic pressure significantly affects its elastic moduli and anisotropic characteristics across the investigated pressure range. The material exhibits the onset of ductility at approximately 7 GPa, which further increases with increasing pressure. At ambient pressure (0 GPa), the optimized structural parameters are in good agreement with previously reported data. Furthermore, the study elucidates the pressure-dependent evolution of structural and electronic properties. Electronic structure analysis confirms the metallic nature of FeSe, with an increase in the density of states (DOS) at the Fermi level under applied pressure, which may contribute to the corresponding enhancement of its superconducting critical temperature. In addition, FeSe exhibits strong optical absorption in both the visible and ultraviolet regions, with absorption coefficients exceeding 10⁵ cm⁻¹.