A New Phase in the Binary Iron Nitrogen System?-The Prediction of Iron Pernitride, FeN2

Among numerous different AB(2) structures with the hypothetical composition FeN2, the structures lying lowest in energy have been determined by a series of density-functional electronic-structure calculations. The most likely FeN2 phase crystallizing in the space group R (3) over barm must be considered an iron pernitride incorporating binuclear N-N units (d = 1.275 angstrom) with an anionic charge of 2-. This high-pressure magnetic phase with a bulk modulus of about 192 GPa and an iron saturation moment of approximately 1.68 mu(B) should already form at a pressure of 17 GPa at an assumed reaction temperature of 1000 K. Besides bonding Fe-N interactions, antibonding N-N and Fe-Fe interactions exist in the crystal structure.