Fe11(NiO3)8 crystallizes in the monoclinic C2/m space group. There are five inequivalent Fe sites. In the first Fe site, Fe(1) is bonded to one O(6), one O(9), and two equivalent O(7) atoms to form distorted FeO4 trigonal pyramids that share  a cornercorner with one Ni(1)O6 octahedra, corners with two equivalent Fe(4)O6 octahedra, corners with two equivalent Ni(4)O6 octahedra, corners with three equivalent Ni(2)O6 octahedra, corners with four equivalent Ni(5)O6 octahedra, and  a faceface with one Ni(3)O6 octahedra. The corner-sharing octahedral tilt angles range from 48-67°. In the second Fe site, Fe(2) is bonded to one O(2), one O(5), and two equivalent O(4) atoms to form FeO4 tetrahedra that share corners with three equivalent Fe(5)O6 octahedra, corners with three equivalent Ni(1)O6 octahedra, and corners with six equivalent Fe(4)O6 octahedra. The corner-sharing octahedral tilt angles range from 54-59°. In the third Fe site, Fe(3) is bonded to one O(3), one O(8), and two equivalent O(1) atoms to form FeO4 tetrahedra that share  a cornercorner with one Ni(4)O6 octahedra, corners with two equivalent Ni(1)O6 octahedra, corners with two equivalent Ni(5)O6 octahedra, corners with three equivalent Ni(2)O6 octahedra, and corners with four equivalent Fe(4)O6 octahedra. The corner-sharing octahedral tilt angles range from 52-63°. In the fourth Fe site, Fe(4) is bonded to one O(1), one O(2), one O(3), one O(4), one O(5), and one O(6) atom to form FeO6 octahedra that share corners with two equivalent Fe(3)O4 tetrahedra, corners with three equivalent Fe(2)O4 tetrahedra,  a cornercorner with one Fe(1)O4 trigonal pyramid,  an edgeedge with one Fe(5)O6 octahedra,  an edgeedge with one Ni(2)O6 octahedra, edges with two equivalent Fe(4)O6 octahedra, and edges with two equivalent Ni(1)O6 octahedra. In the fifth Fe site, Fe(5) is bonded to two equivalent O(5) and four equivalent O(4) atoms to form FeO6 octahedra that share corners with six equivalent Fe(2)O4 tetrahedra, edges with two equivalent Ni(1)O6 octahedra, and edges with four equivalent Fe(4)O6 octahedra. There are five inequivalent Ni sites. In the first Ni site, Ni(1) is bonded to one O(2), one O(6), two equivalent O(1), and two equivalent O(4) atoms to form NiO6 octahedra that share corners with two equivalent Fe(3)O4 tetrahedra, corners with three equivalent Fe(2)O4 tetrahedra,  a cornercorner with one Fe(1)O4 trigonal pyramid,  an edgeedge with one Fe(5)O6 octahedra,  an edgeedge with one Ni(2)O6 octahedra, and edges with four equivalent Fe(4)O6 octahedra. In the second Ni site, Ni(2) is bonded to one O(3), one O(9), two equivalent O(1), and two equivalent O(7) atoms to form NiO6 octahedra that share corners with three equivalent Ni(3)O6 octahedra, corners with three equivalent Fe(3)O4 tetrahedra, corners with three equivalent Fe(1)O4 trigonal pyramids,  an edgeedge with one Ni(1)O6 octahedra,  an edgeedge with one Ni(4)O6 octahedra, edges with two equivalent Fe(4)O6 octahedra, and edges with two equivalent Ni(5)O6 octahedra. The corner-sharing octahedral tilt angles range from 1-2°. In the third Ni site, Ni(3) is bonded to two equivalent O(9) and four equivalent O(7) atoms to form NiO6 octahedra that share corners with six equivalent Ni(2)O6 octahedra, edges with two equivalent Ni(4)O6 octahedra, edges with four equivalent Ni(5)O6 octahedra, and faces with two equivalent Fe(1)O4 trigonal pyramids. The corner-sharing octahedral tilt angles range from 1-2°. In the fourth Ni site, Ni(4) is bonded to two equivalent O(8) and four equivalent O(7) atoms to form NiO6 octahedra that share corners with two equivalent Fe(3)O4 tetrahedra, corners with four equivalent Fe(1)O4 trigonal pyramids, edges with two equivalent Ni(2)O6 octahedra, edges with two equivalent Ni(3)O6 octahedra, and edges with four equivalent Ni(5)O6 octahedra. In the fifth Ni site, Ni(5) is bonded to two equivalent O(7), two equivalent O(8), and two equivalent O(9) atoms to form NiO6 octahedra that share corners with two equivalent Fe(3)O4 tetrahedra, corners with four equivalent Fe(1)O4 trigonal pyramids, edges with two equivalent Ni(2)O6 octahedra, edges with two equivalent Ni(3)O6 octahedra, edges with two equivalent Ni(4)O6 octahedra, and edges with two equivalent Ni(5)O6 octahedra. There are nine inequivalent O sites. In the first O site, O(1) is bonded in a rectangular see-saw-like geometry to one Fe(3), one Fe(4), one Ni(1), and one Ni(2) atom. In the second O site, O(2) is bonded in a rectangular see-saw-like geometry to one Fe(2), two equivalent Fe(4), and one Ni(1) atom. In the third O site, O(3) is bonded in a rectangular see-saw-like geometry to one Fe(3), two equivalent Fe(4), and one Ni(2) atom. In the fourth O site, O(4) is bonded in a rectangular see-saw-like geometry to one Fe(2), one Fe(4), one Fe(5), and one Ni(1) atom. In the fifth O site, O(5) is bonded in a rectangular see-saw-like geometry to one Fe(2), one Fe(5), and two equivalent Fe(4) atoms. In the sixth O site, O(6) is bonded to one Fe(1), two equivalent Fe(4), and one Ni(1) atom to form corner-sharing OFe3Ni tetrahedra. In the seventh O site, O(7) is bonded to one Fe(1), one Ni(2), one Ni(3), one Ni(4), and one Ni(5) atom to form OFeNi4 square pyramids that share corners with three equivalent O(7)FeNi4 square pyramids,  a cornercorner with one O(6)Fe3Ni tetrahedra, edges with three equivalent O(7)FeNi4 square pyramids, and edges with three equivalent O(9)FeNi4 square pyramids. In the eighth O site, O(8) is bonded in a distorted rectangular see-saw-like geometry to one Fe(3), one Ni(4), and two equivalent Ni(5) atoms. In the ninth O site, O(9) is bonded to one Fe(1), one Ni(2), one Ni(3), and two equivalent Ni(5) atoms to form OFeNi4 square pyramids that share corners with three equivalent O(9)FeNi4 square pyramids,  a cornercorner with one O(6)Fe3Ni tetrahedra, and edges with six equivalent O(7)FeNi4 square pyramids.
Fe11(NiO3)8 crystallizes in the monoclinic C2/m space group. There are five inequivalent Fe sites. In the first Fe site, Fe(1) is bonded to one O(6), one O(9), and two equivalent O(7) atoms to form distorted FeO4 trigonal pyramids that share  a cornercorner with one Ni(1)O6 octahedra, corners with two equivalent Fe(4)O6 octahedra, corners with two equivalent Ni(4)O6 octahedra, corners with three equivalent Ni(2)O6 octahedra, corners with four equivalent Ni(5)O6 octahedra, and  a faceface with one Ni(3)O6 octahedra. The corner-sharing octahedral tilt angles range from 48-67°. The Fe(1)-O(6) bond length is 1.84 Å. The Fe(1)-O(9) bond length is 1.97 Å. Both Fe(1)-O(7) bond lengths are 1.97 Å. In the second Fe site, Fe(2) is bonded to one O(2), one O(5), and two equivalent O(4) atoms to form FeO4 tetrahedra that share corners with three equivalent Fe(5)O6 octahedra, corners with three equivalent Ni(1)O6 octahedra, and corners with six equivalent Fe(4)O6 octahedra. The corner-sharing octahedral tilt angles range from 54-59°. The Fe(2)-O(2) bond length is 1.95 Å. The Fe(2)-O(5) bond length is 1.92 Å. Both Fe(2)-O(4) bond lengths are 1.91 Å. In the third Fe site, Fe(3) is bonded to one O(3), one O(8), and two equivalent O(1) atoms to form FeO4 tetrahedra that share  a cornercorner with one Ni(4)O6 octahedra, corners with two equivalent Ni(1)O6 octahedra, corners with two equivalent Ni(5)O6 octahedra, corners with three equivalent Ni(2)O6 octahedra, and corners with four equivalent Fe(4)O6 octahedra. The corner-sharing octahedral tilt angles range from 52-63°. The Fe(3)-O(3) bond length is 1.97 Å. The Fe(3)-O(8) bond length is 1.90 Å. Both Fe(3)-O(1) bond lengths are 1.95 Å. In the fourth Fe site, Fe(4) is bonded to one O(1), one O(2), one O(3), one O(4), one O(5), and one O(6) atom to form FeO6 octahedra that share corners with two equivalent Fe(3)O4 tetrahedra, corners with three equivalent Fe(2)O4 tetrahedra,  a cornercorner with one Fe(1)O4 trigonal pyramid,  an edgeedge with one Fe(5)O6 octahedra,  an edgeedge with one Ni(2)O6 octahedra, edges with two equivalent Fe(4)O6 octahedra, and edges with two equivalent Ni(1)O6 octahedra. The Fe(4)-O(1) bond length is 2.03 Å. The Fe(4)-O(2) bond length is 2.03 Å. The Fe(4)-O(3) bond length is 2.06 Å. The Fe(4)-O(4) bond length is 2.11 Å. The Fe(4)-O(5) bond length is 2.13 Å. The Fe(4)-O(6) bond length is 2.01 Å. In the fifth Fe site, Fe(5) is bonded to two equivalent O(5) and four equivalent O(4) atoms to form FeO6 octahedra that share corners with six equivalent Fe(2)O4 tetrahedra, edges with two equivalent Ni(1)O6 octahedra, and edges with four equivalent Fe(4)O6 octahedra. Both Fe(5)-O(5) bond lengths are 2.04 Å. All Fe(5)-O(4) bond lengths are 2.03 Å. There are five inequivalent Ni sites. In the first Ni site, Ni(1) is bonded to one O(2), one O(6), two equivalent O(1), and two equivalent O(4) atoms to form NiO6 octahedra that share corners with two equivalent Fe(3)O4 tetrahedra, corners with three equivalent Fe(2)O4 tetrahedra,  a cornercorner with one Fe(1)O4 trigonal pyramid,  an edgeedge with one Fe(5)O6 octahedra,  an edgeedge with one Ni(2)O6 octahedra, and edges with four equivalent Fe(4)O6 octahedra. The Ni(1)-O(2) bond length is 2.05 Å. The Ni(1)-O(6) bond length is 2.00 Å. Both Ni(1)-O(1) bond lengths are 2.11 Å. Both Ni(1)-O(4) bond lengths are 2.12 Å. In the second Ni site, Ni(2) is bonded to one O(3), one O(9), two equivalent O(1), and two equivalent O(7) atoms to form NiO6 octahedra that share corners with three equivalent Ni(3)O6 octahedra, corners with three equivalent Fe(3)O4 tetrahedra, corners with three equivalent Fe(1)O4 trigonal pyramids,  an edgeedge with one Ni(1)O6 octahedra,  an edgeedge with one Ni(4)O6 octahedra, edges with two equivalent Fe(4)O6 octahedra, and edges with two equivalent Ni(5)O6 octahedra. The corner-sharing octahedral tilt angles range from 1-2°. The Ni(2)-O(3) bond length is 2.13 Å. The Ni(2)-O(9) bond length is 2.14 Å. Both Ni(2)-O(1) bond lengths are 2.09 Å. Both Ni(2)-O(7) bond lengths are 2.16 Å. In the third Ni site, Ni(3) is bonded to two equivalent O(9) and four equivalent O(7) atoms to form NiO6 octahedra that share corners with six equivalent Ni(2)O6 octahedra, edges with two equivalent Ni(4)O6 octahedra, edges with four equivalent Ni(5)O6 octahedra, and faces with two equivalent Fe(1)O4 trigonal pyramids. The corner-sharing octahedral tilt angles range from 1-2°. Both Ni(3)-O(9) bond lengths are 2.09 Å. All Ni(3)-O(7) bond lengths are 2.10 Å. In the fourth Ni site, Ni(4) is bonded to two equivalent O(8) and four equivalent O(7) atoms to form NiO6 octahedra that share corners with two equivalent Fe(3)O4 tetrahedra, corners with four equivalent Fe(1)O4 trigonal pyramids, edges with two equivalent Ni(2)O6 octahedra, edges with two equivalent Ni(3)O6 octahedra, and edges with four equivalent Ni(5)O6 octahedra. Both Ni(4)-O(8) bond lengths are 2.06 Å. All Ni(4)-O(7) bond lengths are 2.14 Å. In the fifth Ni site, Ni(5) is bonded to two equivalent O(7), two equivalent O(8), and two equivalent O(9) atoms to form NiO6 octahedra that share corners with two equivalent Fe(3)O4 tetrahedra, corners with four equivalent Fe(1)O4 trigonal pyramids, edges with two equivalent Ni(2)O6 octahedra, edges with two equivalent Ni(3)O6 octahedra, edges with two equivalent Ni(4)O6 octahedra, and edges with two equivalent Ni(5)O6 octahedra. Both Ni(5)-O(7) bond lengths are 2.14 Å. Both Ni(5)-O(8) bond lengths are 2.06 Å. Both Ni(5)-O(9) bond lengths are 2.14 Å. There are nine inequivalent O sites. In the first O site, O(1) is bonded in a rectangular see-saw-like geometry to one Fe(3), one Fe(4), one Ni(1), and one Ni(2) atom. In the second O site, O(2) is bonded in a rectangular see-saw-like geometry to one Fe(2), two equivalent Fe(4), and one Ni(1) atom. In the third O site, O(3) is bonded in a rectangular see-saw-like geometry to one Fe(3), two equivalent Fe(4), and one Ni(2) atom. In the fourth O site, O(4) is bonded in a rectangular see-saw-like geometry to one Fe(2), one Fe(4), one Fe(5), and one Ni(1) atom. In the fifth O site, O(5) is bonded in a rectangular see-saw-like geometry to one Fe(2), one Fe(5), and two equivalent Fe(4) atoms. In the sixth O site, O(6) is bonded to one Fe(1), two equivalent Fe(4), and one Ni(1) atom to form corner-sharing OFe3Ni tetrahedra. In the seventh O site, O(7) is bonded to one Fe(1), one Ni(2), one Ni(3), one Ni(4), and one Ni(5) atom to form OFeNi4 square pyramids that share corners with three equivalent O(7)FeNi4 square pyramids,  a cornercorner with one O(6)Fe3Ni tetrahedra, edges with three equivalent O(7)FeNi4 square pyramids, and edges with three equivalent O(9)FeNi4 square pyramids. In the eighth O site, O(8) is bonded in a distorted rectangular see-saw-like geometry to one Fe(3), one Ni(4), and two equivalent Ni(5) atoms. In the ninth O site, O(9) is bonded to one Fe(1), one Ni(2), one Ni(3), and two equivalent Ni(5) atoms to form OFeNi4 square pyramids that share corners with three equivalent O(9)FeNi4 square pyramids,  a cornercorner with one O(6)Fe3Ni tetrahedra, and edges with six equivalent O(7)FeNi4 square pyramids.