Fe14O15 crystallizes in the tetragonal I4/m space group. There are five inequivalent Fe sites. In the first Fe site, Fe(1) is bonded to one O(1), two equivalent O(4), and three equivalent O(2) atoms to form a mixture of edge and corner-sharing FeO6 octahedra. The corner-sharing octahedral tilt angles range from 0-13°. In the second Fe site, Fe(1) is bonded to one O(1), two equivalent O(4), and three equivalent O(2) atoms to form a mixture of edge and corner-sharing FeO6 octahedra. The corner-sharing octahedral tilt angles range from 0-13°. In the third Fe site, Fe(2) is bonded to one O(2), one O(3), and four equivalent O(4) atoms to form a mixture of edge and corner-sharing FeO6 octahedra. The corner-sharing octahedral tilt angles range from 3-13°. In the fourth Fe site, Fe(3) is bonded to one O(1), one O(3), and four equivalent O(4) atoms to form a mixture of edge and corner-sharing FeO6 octahedra. The corner-sharing octahedral tilt angles range from 0-3°. In the fifth Fe site, Fe(1) is bonded to one O(1), two equivalent O(4), and three equivalent O(2) atoms to form a mixture of edge and corner-sharing FeO6 octahedra. The corner-sharing octahedral tilt angles range from 0-13°. There are four inequivalent O sites. In the first O site, O(3) is bonded to one Fe(3) and four equivalent Fe(2) atoms to form OFe5 square pyramids that share  a cornercorner with one O(1)Fe6 octahedra, corners with four equivalent O(4)Fe6 octahedra, corners with four equivalent O(2)Fe5 square pyramids, and edges with eight equivalent O(4)Fe6 octahedra. The corner-sharing octahedral tilt angles range from 0-5°. In the second O site, O(4) is bonded to one Fe(1), one Fe(3), and four equivalent Fe(2) atoms to form OFe6 octahedra that share corners with four equivalent O(4)Fe6 octahedra,  a cornercorner with one O(2)Fe5 square pyramid,  a cornercorner with one O(3)Fe5 square pyramid,  an edgeedge with one O(1)Fe6 octahedra, edges with six equivalent O(4)Fe6 octahedra, edges with two equivalent O(3)Fe5 square pyramids, and edges with three equivalent O(2)Fe5 square pyramids. The corner-sharing octahedral tilt angles range from 1-8°. In the third O site, O(1) is bonded to two equivalent Fe(3) and four Fe(1,1) atoms to form OFe6 octahedra that share corners with two equivalent O(3)Fe5 square pyramids, corners with four equivalent O(2)Fe5 square pyramids, edges with eight equivalent O(4)Fe6 octahedra, and edges with four equivalent O(2)Fe5 square pyramids. In the fourth O site, O(2) is bonded to two equivalent Fe(2) and three Fe(1,1) atoms to form OFe5 square pyramids that share  a cornercorner with one O(1)Fe6 octahedra, corners with two equivalent O(4)Fe6 octahedra, corners with two equivalent O(3)Fe5 square pyramids, corners with four equivalent O(2)Fe5 square pyramids,  an edgeedge with one O(1)Fe6 octahedra, edges with six equivalent O(4)Fe6 octahedra, and  an edgeedge with one O(2)Fe5 square pyramid. The corner-sharing octahedral tilt angles range from 7-10°.
Fe14O15 crystallizes in the tetragonal I4/m space group. There are five inequivalent Fe sites. In the first Fe site, Fe(1) is bonded to one O(1), two equivalent O(4), and three equivalent O(2) atoms to form a mixture of edge and corner-sharing FeO6 octahedra. The corner-sharing octahedral tilt angles range from 0-13°. The Fe(1)-O(1) bond length is 2.22 Å. Both Fe(1)-O(4) bond lengths are 2.14 Å. There are a spread of Fe(1)-O(2) bond distances ranging from 2.07-2.18 Å. In the second Fe site, Fe(1) is bonded to one O(1), two equivalent O(4), and three equivalent O(2) atoms to form a mixture of edge and corner-sharing FeO6 octahedra. The corner-sharing octahedral tilt angles range from 0-13°. The Fe(1)-O(1) bond length is 2.22 Å. Both Fe(1)-O(4) bond lengths are 2.14 Å. There are a spread of Fe(1)-O(2) bond distances ranging from 2.07-2.18 Å. In the third Fe site, Fe(2) is bonded to one O(2), one O(3), and four equivalent O(4) atoms to form a mixture of edge and corner-sharing FeO6 octahedra. The corner-sharing octahedral tilt angles range from 3-13°. The Fe(2)-O(2) bond length is 2.16 Å. The Fe(2)-O(3) bond length is 2.13 Å. There are a spread of Fe(2)-O(4) bond distances ranging from 2.19-2.22 Å. In the fourth Fe site, Fe(3) is bonded to one O(1), one O(3), and four equivalent O(4) atoms to form a mixture of edge and corner-sharing FeO6 octahedra. The corner-sharing octahedral tilt angles range from 0-3°. The Fe(3)-O(1) bond length is 2.11 Å. The Fe(3)-O(3) bond length is 2.02 Å. All Fe(3)-O(4) bond lengths are 2.14 Å. In the fifth Fe site, Fe(1) is bonded to one O(1), two equivalent O(4), and three equivalent O(2) atoms to form a mixture of edge and corner-sharing FeO6 octahedra. The corner-sharing octahedral tilt angles range from 0-13°. The Fe(1)-O(1) bond length is 2.22 Å. Both Fe(1)-O(4) bond lengths are 2.14 Å. There are a spread of Fe(1)-O(2) bond distances ranging from 2.07-2.18 Å. There are four inequivalent O sites. In the first O site, O(3) is bonded to one Fe(3) and four equivalent Fe(2) atoms to form OFe5 square pyramids that share  a cornercorner with one O(1)Fe6 octahedra, corners with four equivalent O(4)Fe6 octahedra, corners with four equivalent O(2)Fe5 square pyramids, and edges with eight equivalent O(4)Fe6 octahedra. The corner-sharing octahedral tilt angles range from 0-5°. In the second O site, O(4) is bonded to one Fe(1), one Fe(3), and four equivalent Fe(2) atoms to form OFe6 octahedra that share corners with four equivalent O(4)Fe6 octahedra,  a cornercorner with one O(2)Fe5 square pyramid,  a cornercorner with one O(3)Fe5 square pyramid,  an edgeedge with one O(1)Fe6 octahedra, edges with six equivalent O(4)Fe6 octahedra, edges with two equivalent O(3)Fe5 square pyramids, and edges with three equivalent O(2)Fe5 square pyramids. The corner-sharing octahedral tilt angles range from 1-8°. In the third O site, O(1) is bonded to two equivalent Fe(3) and four Fe(1,1) atoms to form OFe6 octahedra that share corners with two equivalent O(3)Fe5 square pyramids, corners with four equivalent O(2)Fe5 square pyramids, edges with eight equivalent O(4)Fe6 octahedra, and edges with four equivalent O(2)Fe5 square pyramids. In the fourth O site, O(2) is bonded to two equivalent Fe(2) and three Fe(1,1) atoms to form OFe5 square pyramids that share  a cornercorner with one O(1)Fe6 octahedra, corners with two equivalent O(4)Fe6 octahedra, corners with two equivalent O(3)Fe5 square pyramids, corners with four equivalent O(2)Fe5 square pyramids,  an edgeedge with one O(1)Fe6 octahedra, edges with six equivalent O(4)Fe6 octahedra, and  an edgeedge with one O(2)Fe5 square pyramid. The corner-sharing octahedral tilt angles range from 7-10°.