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Hf3N4 crystallizes in the cubic I-43d space group. The structure is three-dimensional. Hf4+ is bonded in a 8-coordinate geometry to eight equivalent N3- atoms. There are four shorter (2.21 Å) and four longer (2.45 Å) Hf–N bond lengths. N3- is bonded in a 6-coordinate geometry to six equivalent Hf4+ atoms.
Hf3N4 crystallizes in the trigonal R-3m space group. The structure is three-dimensional. there are two inequivalent Hf4+ sites. In the first Hf4+ site, Hf4+ is bonded in a 7-coordinate geometry to seven N3- atoms. There are a spread of Hf–N bond distances ranging from 2.04–2.59 Å. In the second Hf4+ site, Hf4+ is bonded to six equivalent N3- atoms to form edge-sharing HfN6 octahedra. All Hf–N bond lengths are 2.27 Å. There are two inequivalent N3- sites. In the first N3- site, N3- is bonded to six Hf4+ atoms to form distorted NHf6 octahedra that share corners with three equivalent NHf6 octahedra, corners with six equivalent NHf4 tetrahedra, edges with nine equivalent NHf6 octahedra, and edges with three equivalent NHf4 tetrahedra. The corner-sharing octahedral tilt angles are 0°. In the second N3- site, N3- is bonded to four equivalent Hf4+ atoms to form NHf4 tetrahedra that share corners with six equivalent NHf6 octahedra, corners with six equivalent NHf4 tetrahedra, edges with three equivalent NHf6 octahedra, and edges with three equivalent NHf4 tetrahedra. The corner-sharing octahedra tilt angles range from 25–50°.
Hf3N4 is Hausmannite structured and crystallizes in the cubic Fd-3m space group. The structure is three-dimensional. there are two inequivalent Hf4+ sites. In the first Hf4+ site, Hf4+ is bonded to six equivalent N3- atoms to form HfN6 octahedra that share corners with six equivalent HfN4 tetrahedra and edges with six equivalent HfN6 octahedra. All Hf–N bond lengths are 2.20 Å. In the second Hf4+ site, Hf4+ is bonded to four equivalent N3- atoms to form corner-sharing HfN4 tetrahedra. The corner-sharing octahedral tilt angles are 57°. All Hf–N bond lengths are 2.09 Å. N3- is bonded in a distorted rectangular see-saw-like geometry to four Hf4+ atoms.