Structural, mechanical, electronic, and anisotropic properties of niobium-doped strontium ferrite: first-principle calculations

In this research, the various physical properties of Nb-doped SrFeO3 were investigated using the density functional theory (DFT), which was not experimentally investigated and reported in the previous literature. This is the first detailed theoretical study about these properties of this doped system. The calculated lattice parameters exhibited excellent conformity with the experimental data. In addition, the structural and mechanical stability of the studied compound was confirmed by the negative value of formation enthalpy and elastic constants (fulfilled the Born stability criteria), respectively. The metallic nature of SrFe0.5Nb0.5O3 was revealed by their band structure and the density of states. A strong hybridization was observed among Fe-3d, Nb-4p, and O-2p states at the Fermi level, reflecting the covalent bonding of Fe/Nb-O. Furthermore, the mechanical properties including the elastic moduli, Poisson ratio, Pugh's ratio, hardness, and machinability index of SrFe1-xNbxO3 (x=0.4, 0.5, and 0.6), were also studied in depth, and showed considerable effects of doping. Finally, a high level of anisotropy was noticed for SrFe0.5Nb0.5O3. Therefore, our simulation output clearly illustrated the influence of Nb doping in the theoretical results of the physical properties of the presently studied strontium ferrite.