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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.

The atomic arrangement of a model metallic glass Zr2Ni was studied by extended x-ray absorption fine structure and x-ray scattering experiments combined with reverse Monte Carlo simulation imposed an additional potential constraint. By an approach to calculating the free volume (FV) on atomic level, we have found a connection between the coordination number and FV, and then revealed that the atomic structure of Zr2Ni metallic glass is essentially an association of the ordered clusters and FV. The ordered clusters about 1.5 nm consist of a densely packed core (i.e., icosahedral or fcc-type packing) and the surrounding loosely packed clusters with large FV. [ABSTRACT FROM AUTHOR]