The stability, magnetism and electronic structure of Fe ₁₅TMN₂ and Fe₁₄TM₂N₂ (TM=Cr, Mn, Co, and Ni)

The stability, magnetism and electronic structure of Fe ₁₅TMN₂ and Fe₁₄TM₂N₂ (TM=Cr, Mn, Co, and Ni) have been investigated using first-principle electronic structure calculations. The results confirmed that Fe₁₆N₂ is a thermally metastable phase with a tiny positive cohesive energy. However, we found that the few percentage of 3d TM doping could stabilize Fe ₁₆N₂. It indicates that Cr and Mn prefer to occupy 8h and 4e sites of Fe₁₆N₂, respectively, and both of them have straightly bonded to interstitial N. While Co and Ni prefer to occupy the 4d sites, which do not have nearest neighbour N atoms. It is most significant that the total magnetic moments lose little with increasing doping concentration of Mn and Co, up to 12.5%. If these stablest phases are realized in bulk formation, it would be promising for the research of high performance magnetic iron nitride.