Fe3Al5O12 crystallizes in the monoclinic C2/m space group. There are three inequivalent Fe sites. In the first Fe site, Fe(1) is bonded to one O(1), one O(8), and two equivalent O(6) atoms to form FeO4 tetrahedra that share corners with two equivalent Al(1)O6 octahedra, corners with two equivalent Al(3)O6 octahedra, corners with three equivalent Al(4)O6 octahedra, and corners with four equivalent Al(2)O6 octahedra. The corner-sharing octahedral tilt angles range from 55-61°. In the second Fe site, Fe(2) is bonded to one O(2), one O(7), and two equivalent O(5) atoms to form FeO4 tetrahedra that share  a cornercorner with one Al(1)O6 octahedra, corners with two equivalent Al(2)O6 octahedra, corners with three equivalent Al(4)O6 octahedra, and corners with four equivalent Al(3)O6 octahedra. The corner-sharing octahedral tilt angles range from 53-59°. In the third Fe site, Fe(3) is bonded to one O(3), one O(9), and two equivalent O(4) atoms to form FeO4 tetrahedra that share corners with three equivalent Al(1)O6 octahedra and corners with six equivalent Al(2)O6 octahedra. The corner-sharing octahedral tilt angles range from 54-60°. There are four inequivalent Al sites. In the first Al site, Al(1) is bonded to one O(7), one O(9), two equivalent O(4), and two equivalent O(6) atoms to form AlO6 octahedra that share  a cornercorner with one Fe(2)O4 tetrahedra, corners with two equivalent Fe(1)O4 tetrahedra, corners with three equivalent Fe(3)O4 tetrahedra,  an edgeedge with one Al(4)O6 octahedra, and edges with four equivalent Al(2)O6 octahedra. In the second Al site, Al(2) is bonded to one O(1), one O(3), one O(4), one O(6), one O(7), and one O(9) atom to form AlO6 octahedra that share  a cornercorner with one Fe(2)O4 tetrahedra, corners with two equivalent Fe(1)O4 tetrahedra, corners with three equivalent Fe(3)O4 tetrahedra,  an edgeedge with one Al(4)O6 octahedra, edges with two equivalent Al(1)O6 octahedra, and edges with two equivalent Al(2)O6 octahedra. In the third Al site, Al(3) is bonded to two equivalent O(2), two equivalent O(5), and two equivalent O(8) atoms to form AlO6 octahedra that share corners with two equivalent Fe(1)O4 tetrahedra, corners with four equivalent Fe(2)O4 tetrahedra, edges with two equivalent Al(3)O6 octahedra, and edges with two equivalent Al(4)O6 octahedra. In the fourth Al site, Al(4) is bonded to one O(1), one O(2), two equivalent O(5), and two equivalent O(6) atoms to form AlO6 octahedra that share corners with three equivalent Fe(1)O4 tetrahedra, corners with three equivalent Fe(2)O4 tetrahedra,  an edgeedge with one Al(1)O6 octahedra, edges with two equivalent Al(2)O6 octahedra, and edges with two equivalent Al(3)O6 octahedra. There are nine inequivalent O sites. In the first O site, O(1) is bonded to one Fe(1), one Al(4), and two equivalent Al(2) atoms to form a mixture of distorted corner and edge-sharing OAl3Fe tetrahedra. In the second O site, O(2) is bonded in a rectangular see-saw-like geometry to one Fe(2), one Al(4), and two equivalent Al(3) atoms. In the third O site, O(3) is bonded in a trigonal planar geometry to one Fe(3) and two equivalent Al(2) atoms. In the fourth O site, O(4) is bonded in a trigonal planar geometry to one Fe(3), one Al(1), and one Al(2) atom. In the fifth O site, O(5) is bonded in a trigonal planar geometry to one Fe(2), one Al(3), and one Al(4) atom. In the sixth O site, O(6) is bonded to one Fe(1), one Al(1), one Al(2), and one Al(4) atom to form a mixture of distorted corner and edge-sharing OAl3Fe tetrahedra. In the seventh O site, O(7) is bonded in a distorted rectangular see-saw-like geometry to one Fe(2), one Al(1), and two equivalent Al(2) atoms. In the eighth O site, O(8) is bonded in a trigonal planar geometry to one Fe(1) and two equivalent Al(3) atoms. In the ninth O site, O(9) is bonded to one Fe(3), one Al(1), and two equivalent Al(2) atoms to form distorted edge-sharing OAl3Fe tetrahedra.
Fe3Al5O12 crystallizes in the monoclinic C2/m space group. There are three inequivalent Fe sites. In the first Fe site, Fe(1) is bonded to one O(1), one O(8), and two equivalent O(6) atoms to form FeO4 tetrahedra that share corners with two equivalent Al(1)O6 octahedra, corners with two equivalent Al(3)O6 octahedra, corners with three equivalent Al(4)O6 octahedra, and corners with four equivalent Al(2)O6 octahedra. The corner-sharing octahedral tilt angles range from 55-61°. The Fe(1)-O(1) bond length is 1.98 Å. The Fe(1)-O(8) bond length is 1.85 Å. Both Fe(1)-O(6) bond lengths are 1.96 Å. In the second Fe site, Fe(2) is bonded to one O(2), one O(7), and two equivalent O(5) atoms to form FeO4 tetrahedra that share  a cornercorner with one Al(1)O6 octahedra, corners with two equivalent Al(2)O6 octahedra, corners with three equivalent Al(4)O6 octahedra, and corners with four equivalent Al(3)O6 octahedra. The corner-sharing octahedral tilt angles range from 53-59°. The Fe(2)-O(2) bond length is 1.96 Å. The Fe(2)-O(7) bond length is 1.96 Å. Both Fe(2)-O(5) bond lengths are 1.86 Å. In the third Fe site, Fe(3) is bonded to one O(3), one O(9), and two equivalent O(4) atoms to form FeO4 tetrahedra that share corners with three equivalent Al(1)O6 octahedra and corners with six equivalent Al(2)O6 octahedra. The corner-sharing octahedral tilt angles range from 54-60°. The Fe(3)-O(3) bond length is 1.88 Å. The Fe(3)-O(9) bond length is 1.99 Å. Both Fe(3)-O(4) bond lengths are 1.87 Å. There are four inequivalent Al sites. In the first Al site, Al(1) is bonded to one O(7), one O(9), two equivalent O(4), and two equivalent O(6) atoms to form AlO6 octahedra that share  a cornercorner with one Fe(2)O4 tetrahedra, corners with two equivalent Fe(1)O4 tetrahedra, corners with three equivalent Fe(3)O4 tetrahedra,  an edgeedge with one Al(4)O6 octahedra, and edges with four equivalent Al(2)O6 octahedra. The Al(1)-O(7) bond length is 1.96 Å. The Al(1)-O(9) bond length is 1.96 Å. Both Al(1)-O(4) bond lengths are 1.86 Å. Both Al(1)-O(6) bond lengths are 1.97 Å. In the second Al site, Al(2) is bonded to one O(1), one O(3), one O(4), one O(6), one O(7), and one O(9) atom to form AlO6 octahedra that share  a cornercorner with one Fe(2)O4 tetrahedra, corners with two equivalent Fe(1)O4 tetrahedra, corners with three equivalent Fe(3)O4 tetrahedra,  an edgeedge with one Al(4)O6 octahedra, edges with two equivalent Al(1)O6 octahedra, and edges with two equivalent Al(2)O6 octahedra. The Al(2)-O(1) bond length is 2.00 Å. The Al(2)-O(3) bond length is 1.86 Å. The Al(2)-O(4) bond length is 1.86 Å. The Al(2)-O(6) bond length is 1.99 Å. The Al(2)-O(7) bond length is 1.96 Å. The Al(2)-O(9) bond length is 1.94 Å. In the third Al site, Al(3) is bonded to two equivalent O(2), two equivalent O(5), and two equivalent O(8) atoms to form AlO6 octahedra that share corners with two equivalent Fe(1)O4 tetrahedra, corners with four equivalent Fe(2)O4 tetrahedra, edges with two equivalent Al(3)O6 octahedra, and edges with two equivalent Al(4)O6 octahedra. Both Al(3)-O(2) bond lengths are 1.95 Å. Both Al(3)-O(5) bond lengths are 1.91 Å. Both Al(3)-O(8) bond lengths are 1.93 Å. In the fourth Al site, Al(4) is bonded to one O(1), one O(2), two equivalent O(5), and two equivalent O(6) atoms to form AlO6 octahedra that share corners with three equivalent Fe(1)O4 tetrahedra, corners with three equivalent Fe(2)O4 tetrahedra,  an edgeedge with one Al(1)O6 octahedra, edges with two equivalent Al(2)O6 octahedra, and edges with two equivalent Al(3)O6 octahedra. The Al(4)-O(1) bond length is 1.91 Å. The Al(4)-O(2) bond length is 1.97 Å. Both Al(4)-O(5) bond lengths are 1.85 Å. Both Al(4)-O(6) bond lengths are 1.98 Å. There are nine inequivalent O sites. In the first O site, O(1) is bonded to one Fe(1), one Al(4), and two equivalent Al(2) atoms to form a mixture of distorted corner and edge-sharing OAl3Fe tetrahedra. In the second O site, O(2) is bonded in a rectangular see-saw-like geometry to one Fe(2), one Al(4), and two equivalent Al(3) atoms. In the third O site, O(3) is bonded in a trigonal planar geometry to one Fe(3) and two equivalent Al(2) atoms. In the fourth O site, O(4) is bonded in a trigonal planar geometry to one Fe(3), one Al(1), and one Al(2) atom. In the fifth O site, O(5) is bonded in a trigonal planar geometry to one Fe(2), one Al(3), and one Al(4) atom. In the sixth O site, O(6) is bonded to one Fe(1), one Al(1), one Al(2), and one Al(4) atom to form a mixture of distorted corner and edge-sharing OAl3Fe tetrahedra. In the seventh O site, O(7) is bonded in a distorted rectangular see-saw-like geometry to one Fe(2), one Al(1), and two equivalent Al(2) atoms. In the eighth O site, O(8) is bonded in a trigonal planar geometry to one Fe(1) and two equivalent Al(3) atoms. In the ninth O site, O(9) is bonded to one Fe(3), one Al(1), and two equivalent Al(2) atoms to form distorted edge-sharing OAl3Fe tetrahedra.