Stability and magnetism of FeN high-pressure phases.

Most of the experimentally discovered compounds in the iron-nitrogen system belong to the low concentration part of the Fe-N phase diagram. In our paper, which is based on ab initio calculations, we have studied the formation and stability of high-pressure iron mono-nitride phases, and in particular a new magnetic phase with a NiAs-type structure. We have investigated the role of dynamic, thermodynamic and electronic properties, such as electronic correlations and pressure-induced phase stabilisation. Additionally, we have demonstrated that the new hexagonal FeN phase is stable over a wide range of external pressures and can persist at zero pressure as a metastable phase. Further, we have shown that this phase has a relatively low Curie temperature and may possess non-collinear magnetism.