Fe7O8 crystallizes in the cubic Fm-3m space group. There are two inequivalent Fe sites. In the first Fe site, Fe(1) is bonded to two equivalent O(1) and four equivalent O(2) atoms to form a mixture of edge and corner-sharing FeO6 octahedra. The corner-sharing octahedral tilt angles range from 0-6°. In the second Fe site, Fe(2) is bonded to six equivalent O(2) atoms to form edge-sharing FeO6 octahedra. There are two inequivalent O sites. In the first O site, O(2) is bonded to one Fe(2) and four equivalent Fe(1) atoms to form OFe5 square pyramids that share corners with nine equivalent O(2)Fe5 square pyramids, edges with four equivalent O(1)Fe6 octahedra, and edges with four equivalent O(2)Fe5 square pyramids. In the second O site, O(1) is bonded to six equivalent Fe(1) atoms to form OFe6 octahedra that share corners with six equivalent O(1)Fe6 octahedra and edges with twelve equivalent O(2)Fe5 square pyramids. The corner-sharing octahedra are not tilted.
Fe7O8 crystallizes in the cubic Fm-3m space group. There are two inequivalent Fe sites. In the first Fe site, Fe(1) is bonded to two equivalent O(1) and four equivalent O(2) atoms to form a mixture of edge and corner-sharing FeO6 octahedra. The corner-sharing octahedral tilt angles range from 0-6°. Both Fe(1)-O(1) bond lengths are 2.17 Å. All Fe(1)-O(2) bond lengths are 2.17 Å. In the second Fe site, Fe(2) is bonded to six equivalent O(2) atoms to form edge-sharing FeO6 octahedra. All Fe(2)-O(2) bond lengths are 2.05 Å. There are two inequivalent O sites. In the first O site, O(2) is bonded to one Fe(2) and four equivalent Fe(1) atoms to form OFe5 square pyramids that share corners with nine equivalent O(2)Fe5 square pyramids, edges with four equivalent O(1)Fe6 octahedra, and edges with four equivalent O(2)Fe5 square pyramids. In the second O site, O(1) is bonded to six equivalent Fe(1) atoms to form OFe6 octahedra that share corners with six equivalent O(1)Fe6 octahedra and edges with twelve equivalent O(2)Fe5 square pyramids. The corner-sharing octahedra are not tilted.