Fe5NiN4 crystallizes in the orthorhombic Pmmn space group. There are two inequivalent Fe sites. In the first Fe site, Fe(1) is bonded in a 3-coordinate geometry to one N(1) and two equivalent N(2) atoms. In the second Fe site, Fe(2) is bonded to two equivalent N(1) and two equivalent N(2) atoms to form FeN4 tetrahedra that share corners with four equivalent Ni(1)N4 tetrahedra. Ni(1) is bonded to two equivalent N(1) and two equivalent N(2) atoms to form distorted NiN4 tetrahedra that share corners with four equivalent Fe(2)N4 tetrahedra. There are two inequivalent N sites. In the first N site, N(1) is bonded to one Fe(2), two equivalent Fe(1), and one Ni(1) atom to form distorted NFe3Ni tetrahedra that share corners with eight equivalent N(2)Fe5Ni octahedra and corners with two equivalent N(1)Fe3Ni tetrahedra. The corner-sharing octahedral tilt angles range from 44-73°. In the second N site, N(2) is bonded to one Fe(2), four equivalent Fe(1), and one Ni(1) atom to form NFe5Ni octahedra that share corners with two equivalent N(2)Fe5Ni octahedra, corners with eight equivalent N(1)Fe3Ni tetrahedra, and edges with two equivalent N(2)Fe5Ni octahedra. The corner-sharing octahedral tilt angles range from 59-66°.
Fe5NiN4 crystallizes in the orthorhombic Pmmn space group. There are two inequivalent Fe sites. In the first Fe site, Fe(1) is bonded in a 3-coordinate geometry to one N(1) and two equivalent N(2) atoms. The Fe(1)-N(1) bond length is 1.82 Å. There is one shorter (1.87 Å) and one longer (1.91 Å) Fe(1)-N(2) bond length. In the second Fe site, Fe(2) is bonded to two equivalent N(1) and two equivalent N(2) atoms to form FeN4 tetrahedra that share corners with four equivalent Ni(1)N4 tetrahedra. Both Fe(2)-N(1) bond lengths are 1.86 Å. Both Fe(2)-N(2) bond lengths are 1.90 Å. Ni(1) is bonded to two equivalent N(1) and two equivalent N(2) atoms to form distorted NiN4 tetrahedra that share corners with four equivalent Fe(2)N4 tetrahedra. Both Ni(1)-N(1) bond lengths are 1.90 Å. Both Ni(1)-N(2) bond lengths are 2.22 Å. There are two inequivalent N sites. In the first N site, N(1) is bonded to one Fe(2), two equivalent Fe(1), and one Ni(1) atom to form distorted NFe3Ni tetrahedra that share corners with eight equivalent N(2)Fe5Ni octahedra and corners with two equivalent N(1)Fe3Ni tetrahedra. The corner-sharing octahedral tilt angles range from 44-73°. In the second N site, N(2) is bonded to one Fe(2), four equivalent Fe(1), and one Ni(1) atom to form NFe5Ni octahedra that share corners with two equivalent N(2)Fe5Ni octahedra, corners with eight equivalent N(1)Fe3Ni tetrahedra, and edges with two equivalent N(2)Fe5Ni octahedra. The corner-sharing octahedral tilt angles range from 59-66°.