First-principles Study Of Physical Properties And Doping Effects Of Fe 3 Si

Ferromagnetic materials are widely used in daily life,aeronautics and astronautics,national defense,military industry and many other fields.Especially,iron-based alloys have attracted considerable attention for their excellent properties and low price.And D03 type Fe₃ Si alloy,as the most representative material of iron-based alloys,has been a research focus.However,there are only a few studies on the comparison of Fe₃ Si alloy with other iron-based alloys.Besides,doping some elements into a solid is an important research method in chemical industry,materials and so on.Since the properties of adjacent elements are similar in the periodic table.Therefore,Co atoms and Ge atoms are choosed to substitute for Fe atoms and Si atoms in this study,respectively.Herein,in the current work,Fe₃X?X=Si,Ge,Al?alloys,Fe_3-xCo_xSi?x?28?0.00,0.25,0.50,0.75,1.00?alloys and Fe₃Si_1-xGe_x?x?28?0.00,0.25,0.50,0.75,1.00?alloys will be studied as follows based on the first-principles density functional theory:Firstly,the mechanical properties,electronic structures and magnetic properties of Fe₃X?X = Si,Ge,Al?alloys are studied in detail.It can be concluded that all these alloys are ferromagnetic materials with metallic character.And they all have stable cubic structures.Among them,Fe₃ Si can be deemed as the most stable alloy and synthesized easiest.Moreover,it has greater strength,stiffness and hardness but weak plasticity and small total magnetic moment compared with Fe₃ Ge and Fe₃ Al.Secondly,the structures of Fe_3-xCo_xSi?x?28?0.00,0.25,0.50,0.75,1.00?alloys are established and studied based on the experimental results.The calculated cohesive energies indicate that the stabilities of Fe_3-xCo_xSi?x?28?0.00,0.25,0.50,0.75,1.00?alloys prefer to Fe-rich content.It can be concluded that a certain amount of Co doped into Fe₃ Si can enhance its hardness and ability to resist the shear deformation but weaken its plasticity by analyzing mechanical properties.The calculations of electronic structures and magnetic properties reveal that all these five alloys are ferromagnetic materials.Additinally,it can make the Fermi level move towards the conductive bands by doping Co atoms into Fe₃ Si to substitute the preferential sites of Fe atoms,and thus an energy band gap above the Fermi level can be formed in the spin down states of each Fe_3-xCo_xSi?x?28?0.25,0.50,0.75,1.00?alloy,and these band gaps increase with the Co content increasing from 0.25 to 1.00.Generally,there exists strong correlation of 3d electrons in transition-metal atoms.And therefore GGA+U method is also considered in this work to deal with the strong correlation of 3d electrons in Fe atoms and Co atoms.The calculations reveal that the 3d electron correlations of Fe atoms at A and C sites in Fe_3-xCo_xSi?x?28?0.25,0.50,0.75,1.00?alloys are stronger compared with those of Co atoms.Thirdly,the crystal structures of Fe₃Si_1-xGe_x?x = 0.00,0.25,0.50,0.75,1.00?alloys are established and calculated to investigate the effects of Ge dopants on their physical properties.The results show that Ge-doped into Fe₃ Si can enhance the plasticity but weaken the ability to resist shear deformation and its hardness.Besides,the Young's moduli of Fe₃Si_1-xGe_x?x = 0.00,0.25,0.50,0.75,1.00?alloys increase with Ge component increasing,which indicates that the effects between Fe atoms and Si atoms are higher than those between Fe atoms and Ge atoms in Fe₃Si_1-xGe_x?x = 0.00,0.25,0.50,0.75,1.00?alloys.It can be predicted that Ge-doped into Fe₃ Si will become difficult to relaize in experiment with much Ge dopants.Fe₃Si_1-xGe_x?x = 0.00,0.25,0.50,0.75,1.00?alloys all have the stable cubic structures,and their stabilities reduce with Ge increasing.Besides,the calculations of electronic structures reveal that all Fe₃Si_1-xGe_x?x = 0.00,0.25,0.50,0.75,1.00?alloys are magnetic materials with metallic character.And IFe atoms display a larger magnetc moment than IIFe atoms for all cases.With Ge increasing,the magnetc moments of IIFe atoms increase,at the same time,the magnetic moments of IFe,Si and Ge atoms are almost unvaried.This phenomenon leads to an increasing trend of total magnetic moment in Fe₃Si_1-xGe_x?x = 0.00,0.25,0.50,0.75,1.00?alloys as Ge component increasing.