Fe7O8 crystallizes in the triclinic P-1 space group. There are eleven inequivalent Fe sites. In the first Fe site, Fe(1) is bonded to two equivalent O(2), two equivalent O(6), and two equivalent O(8) atoms to form a mixture of corner and edge-sharing FeO6 octahedra. The corner-sharing octahedral tilt angles range from 7-10°. In the second Fe site, Fe(2) is bonded to two equivalent O(1), two equivalent O(5), and two equivalent O(7) atoms to form a mixture of corner and edge-sharing FeO6 octahedra. The corner-sharing octahedral tilt angles range from 6-9°. In the third Fe site, Fe(3) 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 a mixture of corner and edge-sharing FeO6 octahedra. The corner-sharing octahedral tilt angles range from 6-11°. In the fourth Fe site, Fe(4) is bonded to two equivalent O(2), two equivalent O(4), and two equivalent O(6) atoms to form a mixture of corner and edge-sharing FeO6 octahedra. The corner-sharing octahedral tilt angles range from 6-8°. In the fifth Fe site, Fe(5) is bonded to two equivalent O(1), two equivalent O(3), and two equivalent O(5) atoms to form a mixture of corner and edge-sharing FeO6 octahedra. The corner-sharing octahedral tilt angles range from 6-11°. In the sixth Fe site, Fe(6) is bonded to two equivalent O(2), two equivalent O(4), and two equivalent O(8) atoms to form a mixture of corner and edge-sharing FeO6 octahedra. The corner-sharing octahedral tilt angles range from 2-7°. In the seventh Fe site, Fe(7) is bonded to two equivalent O(1), two equivalent O(3), and two equivalent O(7) atoms to form a mixture of corner and edge-sharing FeO6 octahedra. The corner-sharing octahedral tilt angles range from 2-8°. In the eighth Fe site, Fe(8) is bonded to one O(1), one O(2), one O(5), one O(6), one O(7), and one O(8) atom to form a mixture of corner and edge-sharing FeO6 octahedra. The corner-sharing octahedral tilt angles range from 6-10°. In the ninth Fe site, Fe(9) is bonded to one O(1), one O(2), one O(3), one O(4), one O(7), and one O(8) atom to form a mixture of corner and edge-sharing FeO6 octahedra. The corner-sharing octahedral tilt angles range from 2-8°. In the tenth Fe site, Fe(10) is bonded to two equivalent O(4), two equivalent O(6), and two equivalent O(8) atoms to form edge-sharing FeO6 octahedra. In the eleventh Fe site, Fe(11) is bonded to two equivalent O(3), two equivalent O(5), and two equivalent O(7) atoms to form edge-sharing FeO6 octahedra. There are eight inequivalent O sites. In the first O site, O(1) is bonded to one Fe(2), one Fe(3), one Fe(5), one Fe(7), one Fe(8), and one Fe(9) atom to form OFe6 octahedra that share corners with three equivalent O(1)Fe6 octahedra, corners with three equivalent O(2)Fe6 octahedra,  an edgeedge with one O(4)Fe5 square pyramid,  an edgeedge with one O(6)Fe5 square pyramid,  an edgeedge with one O(8)Fe5 square pyramid, edges with three equivalent O(3)Fe5 square pyramids, edges with three equivalent O(5)Fe5 square pyramids, and edges with three equivalent O(7)Fe5 square pyramids. The corner-sharing octahedral tilt angles range from 0-3°. In the second O site, O(2) is bonded to one Fe(1), one Fe(3), one Fe(4), one Fe(6), one Fe(8), and one Fe(9) atom to form OFe6 octahedra that share corners with three equivalent O(1)Fe6 octahedra, corners with three equivalent O(2)Fe6 octahedra,  an edgeedge with one O(3)Fe5 square pyramid,  an edgeedge with one O(5)Fe5 square pyramid,  an edgeedge with one O(7)Fe5 square pyramid, edges with three equivalent O(4)Fe5 square pyramids, edges with three equivalent O(6)Fe5 square pyramids, and edges with three equivalent O(8)Fe5 square pyramids. The corner-sharing octahedral tilt angles range from 0-3°. In the third O site, O(3) is bonded to one Fe(11), one Fe(3), one Fe(5), one Fe(7), and one Fe(9) atom to form OFe5 square pyramids that share  a cornercorner with one O(5)Fe5 square pyramid,  a cornercorner with one O(6)Fe5 square pyramid,  a cornercorner with one O(7)Fe5 square pyramid,  a cornercorner with one O(8)Fe5 square pyramid, corners with two equivalent O(4)Fe5 square pyramids, corners with three equivalent O(3)Fe5 square pyramids,  an edgeedge with one O(2)Fe6 octahedra, edges with three equivalent O(1)Fe6 octahedra, edges with two equivalent O(5)Fe5 square pyramids, and edges with two equivalent O(7)Fe5 square pyramids. In the fourth O site, O(4) is bonded to one Fe(10), one Fe(3), one Fe(4), one Fe(6), and one Fe(9) atom to form OFe5 square pyramids that share  a cornercorner with one O(5)Fe5 square pyramid,  a cornercorner with one O(6)Fe5 square pyramid,  a cornercorner with one O(7)Fe5 square pyramid,  a cornercorner with one O(8)Fe5 square pyramid, corners with two equivalent O(3)Fe5 square pyramids, corners with three equivalent O(4)Fe5 square pyramids,  an edgeedge with one O(1)Fe6 octahedra, edges with three equivalent O(2)Fe6 octahedra, edges with two equivalent O(6)Fe5 square pyramids, and edges with two equivalent O(8)Fe5 square pyramids. In the fifth O site, O(5) is bonded to one Fe(11), one Fe(2), one Fe(3), one Fe(5), and one Fe(8) atom to form OFe5 square pyramids that share  a cornercorner with one O(3)Fe5 square pyramid,  a cornercorner with one O(4)Fe5 square pyramid,  a cornercorner with one O(7)Fe5 square pyramid,  a cornercorner with one O(8)Fe5 square pyramid, corners with two equivalent O(6)Fe5 square pyramids, corners with three equivalent O(5)Fe5 square pyramids,  an edgeedge with one O(2)Fe6 octahedra, edges with three equivalent O(1)Fe6 octahedra, edges with two equivalent O(3)Fe5 square pyramids, and edges with two equivalent O(7)Fe5 square pyramids. In the sixth O site, O(6) is bonded to one Fe(1), one Fe(10), one Fe(3), one Fe(4), and one Fe(8) atom to form OFe5 square pyramids that share  a cornercorner with one O(3)Fe5 square pyramid,  a cornercorner with one O(4)Fe5 square pyramid,  a cornercorner with one O(7)Fe5 square pyramid,  a cornercorner with one O(8)Fe5 square pyramid, corners with two equivalent O(5)Fe5 square pyramids, corners with three equivalent O(6)Fe5 square pyramids,  an edgeedge with one O(1)Fe6 octahedra, edges with three equivalent O(2)Fe6 octahedra, edges with two equivalent O(4)Fe5 square pyramids, and edges with two equivalent O(8)Fe5 square pyramids. In the seventh O site, O(7) is bonded to one Fe(11), one Fe(2), one Fe(7), one Fe(8), and one Fe(9) atom to form OFe5 square pyramids that share  a cornercorner with one O(3)Fe5 square pyramid,  a cornercorner with one O(4)Fe5 square pyramid,  a cornercorner with one O(5)Fe5 square pyramid,  a cornercorner with one O(6)Fe5 square pyramid, corners with two equivalent O(8)Fe5 square pyramids, corners with three equivalent O(7)Fe5 square pyramids,  an edgeedge with one O(2)Fe6 octahedra, edges with three equivalent O(1)Fe6 octahedra, edges with two equivalent O(3)Fe5 square pyramids, and edges with two equivalent O(5)Fe5 square pyramids. In the eighth O site, O(8) is bonded to one Fe(1), one Fe(10), one Fe(6), one Fe(8), and one Fe(9) atom to form OFe5 square pyramids that share  a cornercorner with one O(3)Fe5 square pyramid,  a cornercorner with one O(4)Fe5 square pyramid,  a cornercorner with one O(5)Fe5 square pyramid,  a cornercorner with one O(6)Fe5 square pyramid, corners with two equivalent O(7)Fe5 square pyramids, corners with three equivalent O(8)Fe5 square pyramids,  an edgeedge with one O(1)Fe6 octahedra, edges with three equivalent O(2)Fe6 octahedra, edges with two equivalent O(4)Fe5 square pyramids, and edges with two equivalent O(6)Fe5 square pyramids.
Fe7O8 crystallizes in the triclinic P-1 space group. There are eleven inequivalent Fe sites. In the first Fe site, Fe(1) is bonded to two equivalent O(2), two equivalent O(6), and two equivalent O(8) atoms to form a mixture of corner and edge-sharing FeO6 octahedra. The corner-sharing octahedral tilt angles range from 7-10°. Both Fe(1)-O(2) bond lengths are 2.19 Å. Both Fe(1)-O(6) bond lengths are 2.21 Å. Both Fe(1)-O(8) bond lengths are 2.15 Å. In the second Fe site, Fe(2) is bonded to two equivalent O(1), two equivalent O(5), and two equivalent O(7) atoms to form a mixture of corner and edge-sharing FeO6 octahedra. The corner-sharing octahedral tilt angles range from 6-9°. Both Fe(2)-O(1) bond lengths are 2.16 Å. Both Fe(2)-O(5) bond lengths are 2.27 Å. Both Fe(2)-O(7) bond lengths are 2.12 Å. In the third Fe site, Fe(3) 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 a mixture of corner and edge-sharing FeO6 octahedra. The corner-sharing octahedral tilt angles range from 6-11°. The Fe(3)-O(1) bond length is 2.17 Å. The Fe(3)-O(2) bond length is 2.17 Å. The Fe(3)-O(3) bond length is 2.21 Å. The Fe(3)-O(4) bond length is 2.20 Å. The Fe(3)-O(5) bond length is 2.15 Å. The Fe(3)-O(6) bond length is 2.21 Å. In the fourth Fe site, Fe(4) is bonded to two equivalent O(2), two equivalent O(4), and two equivalent O(6) atoms to form a mixture of corner and edge-sharing FeO6 octahedra. The corner-sharing octahedral tilt angles range from 6-8°. Both Fe(4)-O(2) bond lengths are 2.17 Å. Both Fe(4)-O(4) bond lengths are 2.19 Å. Both Fe(4)-O(6) bond lengths are 2.20 Å. In the fifth Fe site, Fe(5) is bonded to two equivalent O(1), two equivalent O(3), and two equivalent O(5) atoms to form a mixture of corner and edge-sharing FeO6 octahedra. The corner-sharing octahedral tilt angles range from 6-11°. Both Fe(5)-O(1) bond lengths are 2.18 Å. Both Fe(5)-O(3) bond lengths are 2.21 Å. Both Fe(5)-O(5) bond lengths are 2.17 Å. In the sixth Fe site, Fe(6) is bonded to two equivalent O(2), two equivalent O(4), and two equivalent O(8) atoms to form a mixture of corner and edge-sharing FeO6 octahedra. The corner-sharing octahedral tilt angles range from 2-7°. Both Fe(6)-O(2) bond lengths are 2.08 Å. Both Fe(6)-O(4) bond lengths are 2.16 Å. Both Fe(6)-O(8) bond lengths are 2.06 Å. In the seventh Fe site, Fe(7) is bonded to two equivalent O(1), two equivalent O(3), and two equivalent O(7) atoms to form a mixture of corner and edge-sharing FeO6 octahedra. The corner-sharing octahedral tilt angles range from 2-8°. Both Fe(7)-O(1) bond lengths are 2.08 Å. Both Fe(7)-O(3) bond lengths are 2.14 Å. Both Fe(7)-O(7) bond lengths are 2.09 Å. In the eighth Fe site, Fe(8) is bonded to one O(1), one O(2), one O(5), one O(6), one O(7), and one O(8) atom to form a mixture of corner and edge-sharing FeO6 octahedra. The corner-sharing octahedral tilt angles range from 6-10°. The Fe(8)-O(1) bond length is 2.19 Å. The Fe(8)-O(2) bond length is 2.18 Å. The Fe(8)-O(5) bond length is 2.11 Å. The Fe(8)-O(6) bond length is 2.10 Å. The Fe(8)-O(7) bond length is 2.26 Å. The Fe(8)-O(8) bond length is 2.29 Å. In the ninth Fe site, Fe(9) is bonded to one O(1), one O(2), one O(3), one O(4), one O(7), and one O(8) atom to form a mixture of corner and edge-sharing FeO6 octahedra. The corner-sharing octahedral tilt angles range from 2-8°. The Fe(9)-O(1) bond length is 2.32 Å. The Fe(9)-O(2) bond length is 2.32 Å. The Fe(9)-O(3) bond length is 2.20 Å. The Fe(9)-O(4) bond length is 2.20 Å. The Fe(9)-O(7) bond length is 2.32 Å. The Fe(9)-O(8) bond length is 2.25 Å. In the tenth Fe site, Fe(10) is bonded to two equivalent O(4), two equivalent O(6), and two equivalent O(8) atoms to form edge-sharing FeO6 octahedra. Both Fe(10)-O(4) bond lengths are 2.05 Å. Both Fe(10)-O(6) bond lengths are 2.04 Å. Both Fe(10)-O(8) bond lengths are 2.05 Å. In the eleventh Fe site, Fe(11) is bonded to two equivalent O(3), two equivalent O(5), and two equivalent O(7) atoms to form edge-sharing FeO6 octahedra. Both Fe(11)-O(3) bond lengths are 2.05 Å. Both Fe(11)-O(5) bond lengths are 2.03 Å. Both Fe(11)-O(7) bond lengths are 2.05 Å. There are eight inequivalent O sites. In the first O site, O(1) is bonded to one Fe(2), one Fe(3), one Fe(5), one Fe(7), one Fe(8), and one Fe(9) atom to form OFe6 octahedra that share corners with three equivalent O(1)Fe6 octahedra, corners with three equivalent O(2)Fe6 octahedra,  an edgeedge with one O(4)Fe5 square pyramid,  an edgeedge with one O(6)Fe5 square pyramid,  an edgeedge with one O(8)Fe5 square pyramid, edges with three equivalent O(3)Fe5 square pyramids, edges with three equivalent O(5)Fe5 square pyramids, and edges with three equivalent O(7)Fe5 square pyramids. The corner-sharing octahedral tilt angles range from 0-3°. In the second O site, O(2) is bonded to one Fe(1), one Fe(3), one Fe(4), one Fe(6), one Fe(8), and one Fe(9) atom to form OFe6 octahedra that share corners with three equivalent O(1)Fe6 octahedra, corners with three equivalent O(2)Fe6 octahedra,  an edgeedge with one O(3)Fe5 square pyramid,  an edgeedge with one O(5)Fe5 square pyramid,  an edgeedge with one O(7)Fe5 square pyramid, edges with three equivalent O(4)Fe5 square pyramids, edges with three equivalent O(6)Fe5 square pyramids, and edges with three equivalent O(8)Fe5 square pyramids. The corner-sharing octahedral tilt angles range from 0-3°. In the third O site, O(3) is bonded to one Fe(11), one Fe(3), one Fe(5), one Fe(7), and one Fe(9) atom to form OFe5 square pyramids that share  a cornercorner with one O(5)Fe5 square pyramid,  a cornercorner with one O(6)Fe5 square pyramid,  a cornercorner with one O(7)Fe5 square pyramid,  a cornercorner with one O(8)Fe5 square pyramid, corners with two equivalent O(4)Fe5 square pyramids, corners with three equivalent O(3)Fe5 square pyramids,  an edgeedge with one O(2)Fe6 octahedra, edges with three equivalent O(1)Fe6 octahedra, edges with two equivalent O(5)Fe5 square pyramids, and edges with two equivalent O(7)Fe5 square pyramids. In the fourth O site, O(4) is bonded to one Fe(10), one Fe(3), one Fe(4), one Fe(6), and one Fe(9) atom to form OFe5 square pyramids that share  a cornercorner with one O(5)Fe5 square pyramid,  a cornercorner with one O(6)Fe5 square pyramid,  a cornercorner with one O(7)Fe5 square pyramid,  a cornercorner with one O(8)Fe5 square pyramid, corners with two equivalent O(3)Fe5 square pyramids, corners with three equivalent O(4)Fe5 square pyramids,  an edgeedge with one O(1)Fe6 octahedra, edges with three equivalent O(2)Fe6 octahedra, edges with two equivalent O(6)Fe5 square pyramids, and edges with two equivalent O(8)Fe5 square pyramids. In the fifth O site, O(5) is bonded to one Fe(11), one Fe(2), one Fe(3), one Fe(5), and one Fe(8) atom to form OFe5 square pyramids that share  a cornercorner with one O(3)Fe5 square pyramid,  a cornercorner with one O(4)Fe5 square pyramid,  a cornercorner with one O(7)Fe5 square pyramid,  a cornercorner with one O(8)Fe5 square pyramid, corners with two equivalent O(6)Fe5 square pyramids, corners with three equivalent O(5)Fe5 square pyramids,  an edgeedge with one O(2)Fe6 octahedra, edges with three equivalent O(1)Fe6 octahedra, edges with two equivalent O(3)Fe5 square pyramids, and edges with two equivalent O(7)Fe5 square pyramids. In the sixth O site, O(6) is bonded to one Fe(1), one Fe(10), one Fe(3), one Fe(4), and one Fe(8) atom to form OFe5 square pyramids that share  a cornercorner with one O(3)Fe5 square pyramid,  a cornercorner with one O(4)Fe5 square pyramid,  a cornercorner with one O(7)Fe5 square pyramid,  a cornercorner with one O(8)Fe5 square pyramid, corners with two equivalent O(5)Fe5 square pyramids, corners with three equivalent O(6)Fe5 square pyramids,  an edgeedge with one O(1)Fe6 octahedra, edges with three equivalent O(2)Fe6 octahedra, edges with two equivalent O(4)Fe5 square pyramids, and edges with two equivalent O(8)Fe5 square pyramids. In the seventh O site, O(7) is bonded to one Fe(11), one Fe(2), one Fe(7), one Fe(8), and one Fe(9) atom to form OFe5 square pyramids that share  a cornercorner with one O(3)Fe5 square pyramid,  a cornercorner with one O(4)Fe5 square pyramid,  a cornercorner with one O(5)Fe5 square pyramid,  a cornercorner with one O(6)Fe5 square pyramid, corners with two equivalent O(8)Fe5 square pyramids, corners with three equivalent O(7)Fe5 square pyramids,  an edgeedge with one O(2)Fe6 octahedra, edges with three equivalent O(1)Fe6 octahedra, edges with two equivalent O(3)Fe5 square pyramids, and edges with two equivalent O(5)Fe5 square pyramids. In the eighth O site, O(8) is bonded to one Fe(1), one Fe(10), one Fe(6), one Fe(8), and one Fe(9) atom to form OFe5 square pyramids that share  a cornercorner with one O(3)Fe5 square pyramid,  a cornercorner with one O(4)Fe5 square pyramid,  a cornercorner with one O(5)Fe5 square pyramid,  a cornercorner with one O(6)Fe5 square pyramid, corners with two equivalent O(7)Fe5 square pyramids, corners with three equivalent O(8)Fe5 square pyramids,  an edgeedge with one O(1)Fe6 octahedra, edges with three equivalent O(2)Fe6 octahedra, edges with two equivalent O(4)Fe5 square pyramids, and edges with two equivalent O(6)Fe5 square pyramids.