CuAl2O4 is Spinel-like structured and crystallizes in the trigonal P3m1 space group. There are six inequivalent Cu sites. In the first Cu site, Cu(1) is bonded to one O(10) and three equivalent O(1) atoms to form CuO4 tetrahedra that share corners with three equivalent Cu(2)O6 octahedra, corners with three equivalent Al(5)O6 octahedra, and corners with six equivalent Al(1)O6 octahedra. The corner-sharing octahedral tilt angles range from 56-63°. In the second Cu site, Cu(2) is bonded to three equivalent O(1) and three equivalent O(11) atoms to form CuO6 octahedra that share corners with three equivalent Cu(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(5)O6 octahedra. In the third Cu site, Cu(3) is bonded to one O(2) and three equivalent O(3) atoms to form CuO4 tetrahedra that share corners with three equivalent Cu(5)O6 octahedra, 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 57-62°. In the fourth Cu site, Cu(4) is bonded to one O(6) and three equivalent O(8) atoms to form CuO4 tetrahedra that share corners with three equivalent Al(2)O6 octahedra, corners with three equivalent Al(4)O6 octahedra, and corners with six equivalent Al(5)O6 octahedra. The corner-sharing octahedral tilt angles range from 59-60°. In the fifth Cu site, Cu(5) is bonded to three equivalent O(3) and three equivalent O(4) atoms to form CuO6 octahedra that share corners with three equivalent Cu(3)O4 tetrahedra, corners with three equivalent Al(3)O4 tetrahedra, edges with three equivalent Al(1)O6 octahedra, and edges with three equivalent Al(2)O6 octahedra. In the sixth Cu site, Cu(6) is bonded to one O(12) and three equivalent O(7) atoms to form CuO4 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 60-62°. There are six inequivalent Al sites. In the first Al site, Al(1) is bonded to one O(2), one O(5), two equivalent O(1), and two equivalent O(4) atoms to form AlO6 octahedra that share  a cornercorner with one Cu(3)O4 tetrahedra,  a cornercorner with one Al(6)O4 tetrahedra, corners with two equivalent Cu(1)O4 tetrahedra, corners with two equivalent Al(3)O4 tetrahedra,  an edgeedge with one Cu(2)O6 octahedra,  an edgeedge with one Cu(5)O6 octahedra, and edges with four equivalent Al(1)O6 octahedra. In the second Al site, Al(2) is bonded to one O(6), one O(9), two equivalent O(3), and two equivalent O(7) atoms to form AlO6 octahedra that share  a cornercorner with one Cu(4)O4 tetrahedra,  a cornercorner with one Al(3)O4 tetrahedra, corners with two equivalent Cu(3)O4 tetrahedra, corners with two equivalent Cu(6)O4 tetrahedra,  an edgeedge with one Cu(5)O6 octahedra,  an edgeedge with one Al(4)O6 octahedra, and edges with four equivalent Al(2)O6 octahedra. In the third Al site, Al(3) is bonded to one O(9) and three equivalent O(4) atoms to form AlO4 tetrahedra that share corners with three equivalent Cu(5)O6 octahedra, corners with three equivalent Al(2)O6 octahedra, and corners with six equivalent Al(1)O6 octahedra. The corner-sharing octahedral tilt angles range from 55-62°. In the fourth Al site, Al(4) is bonded to three equivalent O(7) and three equivalent O(8) atoms to form AlO6 octahedra that share corners with three equivalent Cu(4)O4 tetrahedra, corners with three equivalent Cu(6)O4 tetrahedra, edges with three equivalent Al(2)O6 octahedra, and edges with three equivalent Al(5)O6 octahedra. In the fifth Al site, Al(5) is bonded to one O(10), one O(12), two equivalent O(11), and two equivalent O(8) atoms to form AlO6 octahedra that share  a cornercorner with one Cu(1)O4 tetrahedra,  a cornercorner with one Cu(6)O4 tetrahedra, corners with two equivalent Cu(4)O4 tetrahedra, corners with two equivalent Al(6)O4 tetrahedra,  an edgeedge with one Cu(2)O6 octahedra,  an edgeedge with one Al(4)O6 octahedra, and edges with four equivalent Al(5)O6 octahedra. In the sixth Al site, Al(6) is bonded to one O(5) and three equivalent O(11) atoms to form AlO4 tetrahedra that share corners with three equivalent Cu(2)O6 octahedra, corners with three equivalent Al(1)O6 octahedra, and corners with six equivalent Al(5)O6 octahedra. The corner-sharing octahedral tilt angles range from 54-61°. There are twelve inequivalent O sites. In the first O site, O(1) is bonded in a rectangular see-saw-like geometry to one Cu(1), one Cu(2), and two equivalent Al(1) atoms. In the second O site, O(2) is bonded in a distorted trigonal pyramidal geometry to one Cu(3) and three equivalent Al(1) atoms. In the third O site, O(3) is bonded in a rectangular see-saw-like geometry to one Cu(3), one Cu(5), and two equivalent Al(2) atoms. In the fourth O site, O(4) is bonded in a rectangular see-saw-like geometry to one Cu(5), one Al(3), and two equivalent Al(1) atoms. In the fifth O site, O(5) is bonded in a distorted rectangular see-saw-like geometry to one Al(6) and three equivalent Al(1) atoms. In the sixth O site, O(6) is bonded to one Cu(4) and three equivalent Al(2) atoms to form distorted corner-sharing OAl3Cu trigonal pyramids. In the seventh O site, O(7) is bonded to one Cu(6), one Al(4), and two equivalent Al(2) atoms to form a mixture of distorted corner and edge-sharing OAl3Cu tetrahedra. In the eighth O site, O(8) is bonded to one Cu(4), one Al(4), and two equivalent Al(5) atoms to form a mixture of distorted corner and edge-sharing OAl3Cu tetrahedra. In the ninth O site, O(9) is bonded in a rectangular see-saw-like geometry to one Al(3) and three equivalent Al(2) atoms. In the tenth O site, O(10) is bonded to one Cu(1) and three equivalent Al(5) atoms to form a mixture of distorted corner and edge-sharing OAl3Cu trigonal pyramids. In the eleventh O site, O(11) is bonded in a rectangular see-saw-like geometry to one Cu(2), one Al(6), and two equivalent Al(5) atoms. In the twelfth O site, O(12) is bonded to one Cu(6) and three equivalent Al(5) atoms to form corner-sharing OAl3Cu tetrahedra.
CuAl2O4 is Spinel-like structured and crystallizes in the trigonal P3m1 space group. There are six inequivalent Cu sites. In the first Cu site, Cu(1) is bonded to one O(10) and three equivalent O(1) atoms to form CuO4 tetrahedra that share corners with three equivalent Cu(2)O6 octahedra, corners with three equivalent Al(5)O6 octahedra, and corners with six equivalent Al(1)O6 octahedra. The corner-sharing octahedral tilt angles range from 56-63°. The Cu(1)-O(10) bond length is 1.97 Å. All Cu(1)-O(1) bond lengths are 1.95 Å. In the second Cu site, Cu(2) is bonded to three equivalent O(1) and three equivalent O(11) atoms to form CuO6 octahedra that share corners with three equivalent Cu(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(5)O6 octahedra. All Cu(2)-O(1) bond lengths are 2.00 Å. All Cu(2)-O(11) bond lengths are 2.10 Å. In the third Cu site, Cu(3) is bonded to one O(2) and three equivalent O(3) atoms to form CuO4 tetrahedra that share corners with three equivalent Cu(5)O6 octahedra, 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 57-62°. The Cu(3)-O(2) bond length is 1.98 Å. All Cu(3)-O(3) bond lengths are 1.94 Å. In the fourth Cu site, Cu(4) is bonded to one O(6) and three equivalent O(8) atoms to form CuO4 tetrahedra that share corners with three equivalent Al(2)O6 octahedra, corners with three equivalent Al(4)O6 octahedra, and corners with six equivalent Al(5)O6 octahedra. The corner-sharing octahedral tilt angles range from 59-60°. The Cu(4)-O(6) bond length is 1.96 Å. All Cu(4)-O(8) bond lengths are 1.97 Å. In the fifth Cu site, Cu(5) is bonded to three equivalent O(3) and three equivalent O(4) atoms to form CuO6 octahedra that share corners with three equivalent Cu(3)O4 tetrahedra, corners with three equivalent Al(3)O4 tetrahedra, edges with three equivalent Al(1)O6 octahedra, and edges with three equivalent Al(2)O6 octahedra. All Cu(5)-O(3) bond lengths are 1.99 Å. All Cu(5)-O(4) bond lengths are 2.11 Å. In the sixth Cu site, Cu(6) is bonded to one O(12) and three equivalent O(7) atoms to form CuO4 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 60-62°. The Cu(6)-O(12) bond length is 2.08 Å. All Cu(6)-O(7) bond lengths are 1.99 Å. There are six inequivalent Al sites. In the first Al site, Al(1) is bonded to one O(2), one O(5), two equivalent O(1), and two equivalent O(4) atoms to form AlO6 octahedra that share  a cornercorner with one Cu(3)O4 tetrahedra,  a cornercorner with one Al(6)O4 tetrahedra, corners with two equivalent Cu(1)O4 tetrahedra, corners with two equivalent Al(3)O4 tetrahedra,  an edgeedge with one Cu(2)O6 octahedra,  an edgeedge with one Cu(5)O6 octahedra, and edges with four equivalent Al(1)O6 octahedra. The Al(1)-O(2) bond length is 1.92 Å. The Al(1)-O(5) bond length is 2.00 Å. Both Al(1)-O(1) bond lengths are 1.89 Å. Both Al(1)-O(4) bond lengths are 1.95 Å. In the second Al site, Al(2) is bonded to one O(6), one O(9), two equivalent O(3), and two equivalent O(7) atoms to form AlO6 octahedra that share  a cornercorner with one Cu(4)O4 tetrahedra,  a cornercorner with one Al(3)O4 tetrahedra, corners with two equivalent Cu(3)O4 tetrahedra, corners with two equivalent Cu(6)O4 tetrahedra,  an edgeedge with one Cu(5)O6 octahedra,  an edgeedge with one Al(4)O6 octahedra, and edges with four equivalent Al(2)O6 octahedra. The Al(2)-O(6) bond length is 1.92 Å. The Al(2)-O(9) bond length is 2.05 Å. Both Al(2)-O(3) bond lengths are 1.90 Å. Both Al(2)-O(7) bond lengths are 1.90 Å. In the third Al site, Al(3) is bonded to one O(9) and three equivalent O(4) atoms to form AlO4 tetrahedra that share corners with three equivalent Cu(5)O6 octahedra, corners with three equivalent Al(2)O6 octahedra, and corners with six equivalent Al(1)O6 octahedra. The corner-sharing octahedral tilt angles range from 55-62°. The Al(3)-O(9) bond length is 1.84 Å. All Al(3)-O(4) bond lengths are 1.84 Å. In the fourth Al site, Al(4) is bonded to three equivalent O(7) and three equivalent O(8) atoms to form AlO6 octahedra that share corners with three equivalent Cu(4)O4 tetrahedra, corners with three equivalent Cu(6)O4 tetrahedra, edges with three equivalent Al(2)O6 octahedra, and edges with three equivalent Al(5)O6 octahedra. All Al(4)-O(7) bond lengths are 1.93 Å. All Al(4)-O(8) bond lengths are 1.92 Å. In the fifth Al site, Al(5) is bonded to one O(10), one O(12), two equivalent O(11), and two equivalent O(8) atoms to form AlO6 octahedra that share  a cornercorner with one Cu(1)O4 tetrahedra,  a cornercorner with one Cu(6)O4 tetrahedra, corners with two equivalent Cu(4)O4 tetrahedra, corners with two equivalent Al(6)O4 tetrahedra,  an edgeedge with one Cu(2)O6 octahedra,  an edgeedge with one Al(4)O6 octahedra, and edges with four equivalent Al(5)O6 octahedra. The Al(5)-O(10) bond length is 1.92 Å. The Al(5)-O(12) bond length is 1.88 Å. Both Al(5)-O(11) bond lengths are 1.98 Å. Both Al(5)-O(8) bond lengths are 1.92 Å. In the sixth Al site, Al(6) is bonded to one O(5) and three equivalent O(11) atoms to form AlO4 tetrahedra that share corners with three equivalent Cu(2)O6 octahedra, corners with three equivalent Al(1)O6 octahedra, and corners with six equivalent Al(5)O6 octahedra. The corner-sharing octahedral tilt angles range from 54-61°. The Al(6)-O(5) bond length is 1.88 Å. All Al(6)-O(11) bond lengths are 1.81 Å. There are twelve inequivalent O sites. In the first O site, O(1) is bonded in a rectangular see-saw-like geometry to one Cu(1), one Cu(2), and two equivalent Al(1) atoms. In the second O site, O(2) is bonded in a distorted trigonal pyramidal geometry to one Cu(3) and three equivalent Al(1) atoms. In the third O site, O(3) is bonded in a rectangular see-saw-like geometry to one Cu(3), one Cu(5), and two equivalent Al(2) atoms. In the fourth O site, O(4) is bonded in a rectangular see-saw-like geometry to one Cu(5), one Al(3), and two equivalent Al(1) atoms. In the fifth O site, O(5) is bonded in a distorted rectangular see-saw-like geometry to one Al(6) and three equivalent Al(1) atoms. In the sixth O site, O(6) is bonded to one Cu(4) and three equivalent Al(2) atoms to form distorted corner-sharing OAl3Cu trigonal pyramids. In the seventh O site, O(7) is bonded to one Cu(6), one Al(4), and two equivalent Al(2) atoms to form a mixture of distorted corner and edge-sharing OAl3Cu tetrahedra. In the eighth O site, O(8) is bonded to one Cu(4), one Al(4), and two equivalent Al(5) atoms to form a mixture of distorted corner and edge-sharing OAl3Cu tetrahedra. In the ninth O site, O(9) is bonded in a rectangular see-saw-like geometry to one Al(3) and three equivalent Al(2) atoms. In the tenth O site, O(10) is bonded to one Cu(1) and three equivalent Al(5) atoms to form a mixture of distorted corner and edge-sharing OAl3Cu trigonal pyramids. In the eleventh O site, O(11) is bonded in a rectangular see-saw-like geometry to one Cu(2), one Al(6), and two equivalent Al(5) atoms. In the twelfth O site, O(12) is bonded to one Cu(6) and three equivalent Al(5) atoms to form corner-sharing OAl3Cu tetrahedra.