A New Structure of the Environment-Friendly Material Fe16N2

In this paper, a new compound c-Fe16N2 is obtained using a new crystal structure prediction software CALYPSO (Crystal Structure Analysis by Particle Swarm Optimization). The compound has a structure of C2/m (the twelfth space group), and a magnetic moment of 17 µB per unit cell. The enthalpy of c-Fe16N2 is - 8.620 eV/atom, which is little to that of α''-Fe16N2 (-8.287 eV/atom), so the former is more stable from the view of energy. The average magnetic moment of c-Fe16N2 is 2.13 µB per iron atom which is small to that of α''- Fe16N2 (2.8 µB). The c-Fe16N2 is a new rare earth-free permanent magnet. No rare earth means no environmental pollution in the the rare earth mining. The α''-Fe16N2 has a highest saturation magnetic flux density, but it is difficult to mass production, because there are other several N-Fe iron compounds (such as Fe3N, Fe4N) in the obtained resultants. The newly found compound c-Fe16N2 may replace α''-Fe16N2 because the former can be easily obtained compared to the latter, and there maybe a new way to mass production of α''-Fe16N2 from c-Fe16N2.