Synthesis of FeN4 at 180 GPa and its crystal structure from a submicron-sized grain

Abstract

Iron tetranitride, FeN 4, was synthesized from the elements in a laser-heated diamond anvil cell at 180 (5) GPa and 2700 (200) K. Its crystal structure was determined based on single-crystal X-ray diffraction data collected from a submicron-sized grain at the synchrotron beamline ID11 of ESRF. The compound crystallizes in the triclinic space group P. In the asymmetric unit, the Fe atom occupies an inversion centre (Wyckoff position 1d), while two N atoms occupy general positions (2i). The structure is made up from edge-sharing [FeN 6 ] octahedra forming chains along [100] and being interconnected through N - N bridges. N atoms form catena-poly[tetraz-1-ene-1,4-diyl] anions [-N=N - N - N-] ∞ 2- running along [001]. In comparison with the previously reported structure of FeN 4 at 135 GPa [Bykov et al. (2018). Nat. Commun. 9, 2756], the crystal structure of FeN 4 at 180 GPa is similar but the structural model is significantly improved in terms of the precision of the bond lengths and angles.