A first-principles study on electronic structures and elastic properties of metal doped α-Fe(N) high nitrogen steel

The binding energies, electronic structures and elastic properties of Ti, V, Cr, Mn, Co, Ni and Mg doped α-Fe(N) systems have been investigated using a first-principles method. The calculated results show that the dopings of Ti, V, Cr and Co improve the stability of α-Fe(N), and the stability of α-Fe(N) is slightly weakened by Mn and Ni, and the doping of Mg is disadvantageous. For Ti, V, Cr and Mn doped α-Fe(N) systems in which the doping metals are on the left side of Fe in the element periodic table and α-Fe(N) systems doped by Co and Ni on the right side of Fe, their corresponding cohesive forces decrease with decreasing atomic radius of the doping species. The obvious interaction exists among M3d, Fe4s3p3d and N2p. In these doping systems, metal atoms lose electrons, while N gains electrons. Dopings of Ti, V, Cr and Mn in α-Fe(N) strengthen the interaction between N and the surrounding metals, and it is not apparent for the dopings of Co, Ni and Mg. Elastic calculations of Fe15 MN systems show that, except for the Fe15 MgN system, shear modulus G and Young modulus E of Fe15 MN systems are improved, and the bulk modulus B slightly decreases, namely, total elastic properties are enhanced. The magnitude change rule of E reflecting the cohesive force between atoms is consistent with that for the binding energies.