Impact of beryllium doping on the structural, electronic and mechanical properties of iron selenide

Density functional theory within the supercell approach is employed in this investigation to examine the structural, electronic, mechanical and thermophysical characteristics of Be-doped iron selenide (FeSe_1−xBe_x) system. The optimized structural attributes of FeSe are observed to be closely aligned with the experimental results, confirming reliability of the approach. The theoretical findings indicate that even a small Be substitution produces notable changes in lattice parameters, bonding geometry, band dispersion and DOS characteristics. Nevertheless, all phases retain metallic behaviour and compositions around x = 0.50, the system undergoes a structural transition from tetragonal symmetry to orthorhombic symmetry. Further, Be content enhanced the N(E_F) and flatter bands support the substantial electronic reconstruction which further indicates that moderate Be incorporation may enhanced T_C and influence pairing-relevant states. Additionally, all phases of FeSe_1−xBe_x (except for x = 0.50, 0.62 & 0.75) meet the mechanical stability requirements, showing high anisotropy and doping dependent alterations in bulk, shear and Young’s moduli. Moreover, lattice stiffening is noted from thoroughly investigated sound velocities, melting and Debye temperature, where the compounds are found to exhibit a higher value at higher Be content. In this instance, most of this research’s conclusions are new as the elastic and thermophysical characteristics are examined for the first time. Thus, these outcomes provide a comprehensive theoretical foundation for understanding alterations brought about by Be in iron chalcogenide systems.