FeAl2O4 is Spinel-like structured and crystallizes in the trigonal P3m1 space group. There are six inequivalent Fe sites. In the first Fe site, Fe(1) is bonded to one O(9) and three equivalent O(1) atoms to form FeO4 tetrahedra that share corners with three equivalent Fe(2)O6 octahedra, corners with three equivalent Al(4)O6 octahedra, and corners with six equivalent Al(1)O6 octahedra. The corner-sharing octahedral tilt angles range from 55-67°. In the second Fe site, Fe(2) is bonded to three equivalent O(1) and three equivalent O(11) atoms to form FeO6 octahedra that share corners with three equivalent Fe(1)O4 tetrahedra, corners with three equivalent Al(6)O4 tetrahedra, edges with three equivalent Al(1)O6 octahedra, and edges with three equivalent Al(4)O6 octahedra. In the third Fe site, Fe(3) is bonded to one O(2) and three equivalent O(3) atoms to form FeO4 tetrahedra that share corners with three equivalent Al(1)O6 octahedra, corners with three equivalent Al(3)O6 octahedra, and corners with six equivalent Al(2)O6 octahedra. The corner-sharing octahedral tilt angles range from 59-61°. In the fourth Fe site, Fe(4) is bonded to one O(5) and three equivalent O(7) atoms to form FeO4 tetrahedra that share corners with three equivalent Al(2)O6 octahedra, corners with three equivalent Al(5)O6 octahedra, and corners with six equivalent Al(4)O6 octahedra. The corner-sharing octahedral tilt angles are 60°. In the fifth Fe site, Fe(5) is bonded to one O(10) and three equivalent O(4) atoms to form FeO4 tetrahedra that share corners with three equivalent Al(2)O6 octahedra, corners with three equivalent Al(3)O6 octahedra, and corners with six equivalent Al(1)O6 octahedra. The corner-sharing octahedral tilt angles range from 59-63°. In the sixth Fe site, Fe(6) is bonded to one O(12) and three equivalent O(8) atoms to form FeO4 tetrahedra that share corners with three equivalent Al(4)O6 octahedra, corners with three equivalent Al(5)O6 octahedra, and corners with six equivalent Al(2)O6 octahedra. The corner-sharing octahedral tilt angles range from 60-63°. There are six inequivalent Al sites. In the first Al site, Al(1) is bonded to one O(2), one O(6), two equivalent O(1), and two equivalent O(4) atoms to form AlO6 octahedra that share  a cornercorner with one Fe(3)O4 tetrahedra,  a cornercorner with one Al(6)O4 tetrahedra, corners with two equivalent Fe(1)O4 tetrahedra, corners with two equivalent Fe(5)O4 tetrahedra,  an edgeedge with one Fe(2)O6 octahedra,  an edgeedge with one Al(3)O6 octahedra, and edges with four equivalent Al(1)O6 octahedra. In the second Al site, Al(2) is bonded to one O(10), one O(5), two equivalent O(3), and two equivalent O(8) atoms to form AlO6 octahedra that share  a cornercorner with one Fe(4)O4 tetrahedra,  a cornercorner with one Fe(5)O4 tetrahedra, corners with two equivalent Fe(3)O4 tetrahedra, corners with two equivalent Fe(6)O4 tetrahedra,  an edgeedge with one Al(3)O6 octahedra,  an edgeedge with one Al(5)O6 octahedra, and edges with four equivalent Al(2)O6 octahedra. In the third Al site, Al(3) is bonded to three equivalent O(3) and three equivalent O(4) atoms to form AlO6 octahedra that share corners with three equivalent Fe(3)O4 tetrahedra, corners with three equivalent Fe(5)O4 tetrahedra, edges with three equivalent Al(1)O6 octahedra, and edges with three equivalent Al(2)O6 octahedra. In the fourth Al site, Al(4) is bonded to one O(12), one O(9), two equivalent O(11), and two equivalent O(7) atoms to form AlO6 octahedra that share  a cornercorner with one Fe(1)O4 tetrahedra,  a cornercorner with one Fe(6)O4 tetrahedra, corners with two equivalent Fe(4)O4 tetrahedra, corners with two equivalent Al(6)O4 tetrahedra,  an edgeedge with one Fe(2)O6 octahedra,  an edgeedge with one Al(5)O6 octahedra, and edges with four equivalent Al(4)O6 octahedra. In the fifth Al site, Al(5) is bonded to three equivalent O(7) and three equivalent O(8) atoms to form AlO6 octahedra that share corners with three equivalent Fe(4)O4 tetrahedra, corners with three equivalent Fe(6)O4 tetrahedra, edges with three equivalent Al(2)O6 octahedra, and edges with three equivalent Al(4)O6 octahedra. In the sixth Al site, Al(6) is bonded to one O(6) and three equivalent O(11) atoms to form AlO4 tetrahedra that share corners with three equivalent Fe(2)O6 octahedra, corners with three equivalent Al(1)O6 octahedra, and corners with six equivalent Al(4)O6 octahedra. The corner-sharing octahedral tilt angles range from 54-62°. There are twelve inequivalent O sites. In the first O site, O(1) is bonded in a distorted rectangular see-saw-like geometry to one Fe(1), one Fe(2), and two equivalent Al(1) atoms. In the second O site, O(2) is bonded to one Fe(3) and three equivalent Al(1) atoms to form distorted corner-sharing OAl3Fe trigonal pyramids. In the third O site, O(3) is bonded to one Fe(3), one Al(3), and two equivalent Al(2) atoms to form a mixture of distorted edge and corner-sharing OAl3Fe tetrahedra. In the fourth O site, O(4) is bonded to one Fe(5), one Al(3), and two equivalent Al(1) atoms to form a mixture of edge and corner-sharing OAl3Fe tetrahedra. In the fifth O site, O(5) is bonded to one Fe(4) and three equivalent Al(2) atoms to form a mixture of distorted edge and corner-sharing OAl3Fe tetrahedra. In the sixth O site, O(6) is bonded in a distorted rectangular see-saw-like geometry to one Al(6) and three equivalent Al(1) atoms. In the seventh O site, O(7) is bonded to one Fe(4), one Al(5), and two equivalent Al(4) atoms to form a mixture of distorted edge and corner-sharing OAl3Fe tetrahedra. In the eighth O site, O(8) is bonded to one Fe(6), one Al(5), and two equivalent Al(2) atoms to form a mixture of distorted edge and corner-sharing OAl3Fe tetrahedra. In the ninth O site, O(9) is bonded to one Fe(1) and three equivalent Al(4) atoms to form a mixture of distorted edge and corner-sharing OAl3Fe trigonal pyramids. In the tenth O site, O(10) is bonded to one Fe(5) and three equivalent Al(2) atoms to form a mixture of distorted edge and corner-sharing OAl3Fe tetrahedra. In the eleventh O site, O(11) is bonded in a rectangular see-saw-like geometry to one Fe(2), one Al(6), and two equivalent Al(4) atoms. In the twelfth O site, O(12) is bonded to one Fe(6) and three equivalent Al(4) atoms to form corner-sharing OAl3Fe tetrahedra.
FeAl2O4 is Spinel-like structured and crystallizes in the trigonal P3m1 space group. There are six inequivalent Fe sites. In the first Fe site, Fe(1) is bonded to one O(9) and three equivalent O(1) atoms to form FeO4 tetrahedra that share corners with three equivalent Fe(2)O6 octahedra, corners with three equivalent Al(4)O6 octahedra, and corners with six equivalent Al(1)O6 octahedra. The corner-sharing octahedral tilt angles range from 55-67°. The Fe(1)-O(9) bond length is 2.03 Å. All Fe(1)-O(1) bond lengths are 1.97 Å. In the second Fe site, Fe(2) is bonded to three equivalent O(1) and three equivalent O(11) atoms to form FeO6 octahedra that share corners with three equivalent Fe(1)O4 tetrahedra, corners with three equivalent Al(6)O4 tetrahedra, edges with three equivalent Al(1)O6 octahedra, and edges with three equivalent Al(4)O6 octahedra. All Fe(2)-O(1) bond lengths are 2.11 Å. All Fe(2)-O(11) bond lengths are 2.17 Å. In the third Fe site, Fe(3) is bonded to one O(2) and three equivalent O(3) atoms to form FeO4 tetrahedra that share corners with three equivalent Al(1)O6 octahedra, corners with three equivalent Al(3)O6 octahedra, and corners with six equivalent Al(2)O6 octahedra. The corner-sharing octahedral tilt angles range from 59-61°. The Fe(3)-O(2) bond length is 1.98 Å. All Fe(3)-O(3) bond lengths are 2.01 Å. In the fourth Fe site, Fe(4) is bonded to one O(5) and three equivalent O(7) atoms to form FeO4 tetrahedra that share corners with three equivalent Al(2)O6 octahedra, corners with three equivalent Al(5)O6 octahedra, and corners with six equivalent Al(4)O6 octahedra. The corner-sharing octahedral tilt angles are 60°. The Fe(4)-O(5) bond length is 2.00 Å. All Fe(4)-O(7) bond lengths are 2.01 Å. In the fifth Fe site, Fe(5) is bonded to one O(10) and three equivalent O(4) atoms to form FeO4 tetrahedra that share corners with three equivalent Al(2)O6 octahedra, corners with three equivalent Al(3)O6 octahedra, and corners with six equivalent Al(1)O6 octahedra. The corner-sharing octahedral tilt angles range from 59-63°. The Fe(5)-O(10) bond length is 2.06 Å. All Fe(5)-O(4) bond lengths are 2.02 Å. In the sixth Fe site, Fe(6) is bonded to one O(12) and three equivalent O(8) atoms to form FeO4 tetrahedra that share corners with three equivalent Al(4)O6 octahedra, corners with three equivalent Al(5)O6 octahedra, and corners with six equivalent Al(2)O6 octahedra. The corner-sharing octahedral tilt angles range from 60-63°. The Fe(6)-O(12) bond length is 2.07 Å. All Fe(6)-O(8) bond lengths are 2.03 Å. There are six inequivalent Al sites. In the first Al site, Al(1) is bonded to one O(2), one O(6), two equivalent O(1), and two equivalent O(4) atoms to form AlO6 octahedra that share  a cornercorner with one Fe(3)O4 tetrahedra,  a cornercorner with one Al(6)O4 tetrahedra, corners with two equivalent Fe(1)O4 tetrahedra, corners with two equivalent Fe(5)O4 tetrahedra,  an edgeedge with one Fe(2)O6 octahedra,  an edgeedge with one Al(3)O6 octahedra, and edges with four equivalent Al(1)O6 octahedra. The Al(1)-O(2) bond length is 1.93 Å. The Al(1)-O(6) bond length is 2.10 Å. Both Al(1)-O(1) bond lengths are 1.88 Å. Both Al(1)-O(4) bond lengths are 1.94 Å. In the second Al site, Al(2) is bonded to one O(10), one O(5), two equivalent O(3), and two equivalent O(8) atoms to form AlO6 octahedra that share  a cornercorner with one Fe(4)O4 tetrahedra,  a cornercorner with one Fe(5)O4 tetrahedra, corners with two equivalent Fe(3)O4 tetrahedra, corners with two equivalent Fe(6)O4 tetrahedra,  an edgeedge with one Al(3)O6 octahedra,  an edgeedge with one Al(5)O6 octahedra, and edges with four equivalent Al(2)O6 octahedra. The Al(2)-O(10) bond length is 1.92 Å. The Al(2)-O(5) bond length is 1.97 Å. Both Al(2)-O(3) bond lengths are 1.93 Å. Both Al(2)-O(8) bond lengths are 1.93 Å. In the third Al site, Al(3) is bonded to three equivalent O(3) and three equivalent O(4) atoms to form AlO6 octahedra that share corners with three equivalent Fe(3)O4 tetrahedra, corners with three equivalent Fe(5)O4 tetrahedra, edges with three equivalent Al(1)O6 octahedra, and edges with three equivalent Al(2)O6 octahedra. All Al(3)-O(3) bond lengths are 1.95 Å. All Al(3)-O(4) bond lengths are 1.92 Å. In the fourth Al site, Al(4) is bonded to one O(12), one O(9), two equivalent O(11), and two equivalent O(7) atoms to form AlO6 octahedra that share  a cornercorner with one Fe(1)O4 tetrahedra,  a cornercorner with one Fe(6)O4 tetrahedra, corners with two equivalent Fe(4)O4 tetrahedra, corners with two equivalent Al(6)O4 tetrahedra,  an edgeedge with one Fe(2)O6 octahedra,  an edgeedge with one Al(5)O6 octahedra, and edges with four equivalent Al(4)O6 octahedra. The Al(4)-O(12) bond length is 1.92 Å. The Al(4)-O(9) bond length is 1.93 Å. Both Al(4)-O(11) bond lengths are 2.00 Å. Both Al(4)-O(7) bond lengths are 1.93 Å. In the fifth Al site, Al(5) is bonded to three equivalent O(7) and three equivalent O(8) atoms to form AlO6 octahedra that share corners with three equivalent Fe(4)O4 tetrahedra, corners with three equivalent Fe(6)O4 tetrahedra, edges with three equivalent Al(2)O6 octahedra, and edges with three equivalent Al(4)O6 octahedra. All Al(5)-O(7) bond lengths are 1.94 Å. All Al(5)-O(8) bond lengths are 1.92 Å. In the sixth Al site, Al(6) is bonded to one O(6) and three equivalent O(11) atoms to form AlO4 tetrahedra that share corners with three equivalent Fe(2)O6 octahedra, corners with three equivalent Al(1)O6 octahedra, and corners with six equivalent Al(4)O6 octahedra. The corner-sharing octahedral tilt angles range from 54-62°. The Al(6)-O(6) bond length is 1.84 Å. All Al(6)-O(11) bond lengths are 1.83 Å. There are twelve inequivalent O sites. In the first O site, O(1) is bonded in a distorted rectangular see-saw-like geometry to one Fe(1), one Fe(2), and two equivalent Al(1) atoms. In the second O site, O(2) is bonded to one Fe(3) and three equivalent Al(1) atoms to form distorted corner-sharing OAl3Fe trigonal pyramids. In the third O site, O(3) is bonded to one Fe(3), one Al(3), and two equivalent Al(2) atoms to form a mixture of distorted edge and corner-sharing OAl3Fe tetrahedra. In the fourth O site, O(4) is bonded to one Fe(5), one Al(3), and two equivalent Al(1) atoms to form a mixture of edge and corner-sharing OAl3Fe tetrahedra. In the fifth O site, O(5) is bonded to one Fe(4) and three equivalent Al(2) atoms to form a mixture of distorted edge and corner-sharing OAl3Fe tetrahedra. In the sixth O site, O(6) is bonded in a distorted rectangular see-saw-like geometry to one Al(6) and three equivalent Al(1) atoms. In the seventh O site, O(7) is bonded to one Fe(4), one Al(5), and two equivalent Al(4) atoms to form a mixture of distorted edge and corner-sharing OAl3Fe tetrahedra. In the eighth O site, O(8) is bonded to one Fe(6), one Al(5), and two equivalent Al(2) atoms to form a mixture of distorted edge and corner-sharing OAl3Fe tetrahedra. In the ninth O site, O(9) is bonded to one Fe(1) and three equivalent Al(4) atoms to form a mixture of distorted edge and corner-sharing OAl3Fe trigonal pyramids. In the tenth O site, O(10) is bonded to one Fe(5) and three equivalent Al(2) atoms to form a mixture of distorted edge and corner-sharing OAl3Fe tetrahedra. In the eleventh O site, O(11) is bonded in a rectangular see-saw-like geometry to one Fe(2), one Al(6), and two equivalent Al(4) atoms. In the twelfth O site, O(12) is bonded to one Fe(6) and three equivalent Al(4) atoms to form corner-sharing OAl3Fe tetrahedra.