  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 formation and stability of
high-pressure iron mono-nitride phases, and particularly the 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. We demonstrate that the new hexagonal FeN
phase is stable for a wide range of external pressure and it can be formed as a
metastable phase at zero pressure. We show that it has relativity small Curie
temperature and it may possess a non-collinear magnetism.
