NiAl2O4 is Spinel structured and crystallizes in the triclinic P1 space group. There are two inequivalent Ni sites. In the first Ni site, Ni(1) is bonded to one O(2), one O(4), one O(7), and one O(8) atom to form NiO4 tetrahedra that share corners with three equivalent Al(1)O6 octahedra, corners with three equivalent Al(2)O6 octahedra, corners with three equivalent Al(3)O6 octahedra, and corners with three equivalent Al(4)O6 octahedra. The corner-sharing octahedral tilt angles range from 58-62°. In the second Ni site, Ni(2) is bonded to one O(1), one O(3), one O(5), and one O(6) atom to form NiO4 tetrahedra that share corners with three equivalent Al(1)O6 octahedra, corners with three equivalent Al(2)O6 octahedra, corners with three equivalent Al(3)O6 octahedra, and corners with three equivalent Al(4)O6 octahedra. The corner-sharing octahedral tilt angles range from 58-62°. There are four inequivalent Al sites. In the first Al site, Al(1) is bonded to one O(1), one O(2), one O(5), one O(6), one O(7), and one O(8) atom to form AlO6 octahedra that share corners with three equivalent Ni(1)O4 tetrahedra, corners with three equivalent Ni(2)O4 tetrahedra, edges with two equivalent Al(2)O6 octahedra, edges with two equivalent Al(3)O6 octahedra, and edges with two equivalent Al(4)O6 octahedra. In the second Al site, Al(2) is bonded to one O(3), one O(4), one O(5), one O(6), one O(7), and one O(8) atom to form AlO6 octahedra that share corners with three equivalent Ni(1)O4 tetrahedra, corners with three equivalent Ni(2)O4 tetrahedra, edges with two equivalent Al(1)O6 octahedra, edges with two equivalent Al(3)O6 octahedra, and edges with two equivalent Al(4)O6 octahedra. In the third Al site, Al(3) is bonded to one O(1), one O(2), one O(3), one O(4), one O(6), and one O(7) atom to form AlO6 octahedra that share corners with three equivalent Ni(1)O4 tetrahedra, corners with three equivalent Ni(2)O4 tetrahedra, edges with two equivalent Al(1)O6 octahedra, edges with two equivalent Al(2)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), one O(3), one O(4), one O(5), and one O(8) atom to form AlO6 octahedra that share corners with three equivalent Ni(1)O4 tetrahedra, corners with three equivalent Ni(2)O4 tetrahedra, edges with two equivalent Al(1)O6 octahedra, edges with two equivalent Al(2)O6 octahedra, and edges with two equivalent Al(3)O6 octahedra. There are eight inequivalent O sites. In the first O site, O(1) is bonded to one Ni(2), one Al(1), one Al(3), and one Al(4) atom to form a mixture of distorted corner and edge-sharing OAl3Ni tetrahedra. In the second O site, O(2) is bonded to one Ni(1), one Al(1), one Al(3), and one Al(4) atom to form a mixture of distorted corner and edge-sharing OAl3Ni trigonal pyramids. In the third O site, O(3) is bonded to one Ni(2), one Al(2), one Al(3), and one Al(4) atom to form a mixture of distorted corner and edge-sharing OAl3Ni trigonal pyramids. In the fourth O site, O(4) is bonded to one Ni(1), one Al(2), one Al(3), and one Al(4) atom to form a mixture of distorted corner and edge-sharing OAl3Ni tetrahedra. In the fifth O site, O(5) is bonded to one Ni(2), one Al(1), one Al(2), and one Al(4) atom to form a mixture of distorted corner and edge-sharing OAl3Ni trigonal pyramids. In the sixth O site, O(6) is bonded to one Ni(2), one Al(1), one Al(2), and one Al(3) atom to form a mixture of distorted corner and edge-sharing OAl3Ni tetrahedra. In the seventh O site, O(7) is bonded to one Ni(1), one Al(1), one Al(2), and one Al(3) atom to form a mixture of distorted corner and edge-sharing OAl3Ni trigonal pyramids. In the eighth O site, O(8) is bonded to one Ni(1), one Al(1), one Al(2), and one Al(4) atom to form a mixture of distorted corner and edge-sharing OAl3Ni trigonal pyramids.
NiAl2O4 is Spinel structured and crystallizes in the triclinic P1 space group. There are two inequivalent Ni sites. In the first Ni site, Ni(1) is bonded to one O(2), one O(4), one O(7), and one O(8) atom to form NiO4 tetrahedra that share corners with three equivalent Al(1)O6 octahedra, corners with three equivalent Al(2)O6 octahedra, corners with three equivalent Al(3)O6 octahedra, and corners with three equivalent Al(4)O6 octahedra. The corner-sharing octahedral tilt angles range from 58-62°. The Ni(1)-O(2) bond length is 1.98 Å. The Ni(1)-O(4) bond length is 1.97 Å. The Ni(1)-O(7) bond length is 1.98 Å. The Ni(1)-O(8) bond length is 1.96 Å. In the second Ni site, Ni(2) is bonded to one O(1), one O(3), one O(5), and one O(6) atom to form NiO4 tetrahedra that share corners with three equivalent Al(1)O6 octahedra, corners with three equivalent Al(2)O6 octahedra, corners with three equivalent Al(3)O6 octahedra, and corners with three equivalent Al(4)O6 octahedra. The corner-sharing octahedral tilt angles range from 58-62°. The Ni(2)-O(1) bond length is 1.96 Å. The Ni(2)-O(3) bond length is 1.99 Å. The Ni(2)-O(5) bond length is 1.97 Å. The Ni(2)-O(6) bond length is 1.97 Å. There are four inequivalent Al sites. In the first Al site, Al(1) is bonded to one O(1), one O(2), one O(5), one O(6), one O(7), and one O(8) atom to form AlO6 octahedra that share corners with three equivalent Ni(1)O4 tetrahedra, corners with three equivalent Ni(2)O4 tetrahedra, edges with two equivalent Al(2)O6 octahedra, edges with two equivalent Al(3)O6 octahedra, and edges with two equivalent Al(4)O6 octahedra. The Al(1)-O(1) bond length is 1.93 Å. The Al(1)-O(2) bond length is 1.95 Å. The Al(1)-O(5) bond length is 1.93 Å. The Al(1)-O(6) bond length is 1.92 Å. The Al(1)-O(7) bond length is 1.94 Å. The Al(1)-O(8) bond length is 1.95 Å. In the second Al site, Al(2) is bonded to one O(3), one O(4), one O(5), one O(6), one O(7), and one O(8) atom to form AlO6 octahedra that share corners with three equivalent Ni(1)O4 tetrahedra, corners with three equivalent Ni(2)O4 tetrahedra, edges with two equivalent Al(1)O6 octahedra, edges with two equivalent Al(3)O6 octahedra, and edges with two equivalent Al(4)O6 octahedra. The Al(2)-O(3) bond length is 1.94 Å. The Al(2)-O(4) bond length is 1.92 Å. The Al(2)-O(5) bond length is 1.95 Å. The Al(2)-O(6) bond length is 1.94 Å. The Al(2)-O(7) bond length is 1.92 Å. The Al(2)-O(8) bond length is 1.93 Å. In the third Al site, Al(3) is bonded to one O(1), one O(2), one O(3), one O(4), one O(6), and one O(7) atom to form AlO6 octahedra that share corners with three equivalent Ni(1)O4 tetrahedra, corners with three equivalent Ni(2)O4 tetrahedra, edges with two equivalent Al(1)O6 octahedra, edges with two equivalent Al(2)O6 octahedra, and edges with two equivalent Al(4)O6 octahedra. The Al(3)-O(1) bond length is 1.93 Å. The Al(3)-O(2) bond length is 1.94 Å. The Al(3)-O(3) bond length is 1.93 Å. The Al(3)-O(4) bond length is 1.93 Å. The Al(3)-O(6) bond length is 1.92 Å. The Al(3)-O(7) bond length is 1.93 Å. In the fourth Al site, Al(4) is bonded to one O(1), one O(2), one O(3), one O(4), one O(5), and one O(8) atom to form AlO6 octahedra that share corners with three equivalent Ni(1)O4 tetrahedra, corners with three equivalent Ni(2)O4 tetrahedra, edges with two equivalent 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 1.94 Å. The Al(4)-O(2) bond length is 1.93 Å. The Al(4)-O(3) bond length is 1.94 Å. The Al(4)-O(4) bond length is 1.93 Å. The Al(4)-O(5) bond length is 1.95 Å. The Al(4)-O(8) bond length is 1.94 Å. There are eight inequivalent O sites. In the first O site, O(1) is bonded to one Ni(2), one Al(1), one Al(3), and one Al(4) atom to form a mixture of distorted corner and edge-sharing OAl3Ni tetrahedra. In the second O site, O(2) is bonded to one Ni(1), one Al(1), one Al(3), and one Al(4) atom to form a mixture of distorted corner and edge-sharing OAl3Ni trigonal pyramids. In the third O site, O(3) is bonded to one Ni(2), one Al(2), one Al(3), and one Al(4) atom to form a mixture of distorted corner and edge-sharing OAl3Ni trigonal pyramids. In the fourth O site, O(4) is bonded to one Ni(1), one Al(2), one Al(3), and one Al(4) atom to form a mixture of distorted corner and edge-sharing OAl3Ni tetrahedra. In the fifth O site, O(5) is bonded to one Ni(2), one Al(1), one Al(2), and one Al(4) atom to form a mixture of distorted corner and edge-sharing OAl3Ni trigonal pyramids. In the sixth O site, O(6) is bonded to one Ni(2), one Al(1), one Al(2), and one Al(3) atom to form a mixture of distorted corner and edge-sharing OAl3Ni tetrahedra. In the seventh O site, O(7) is bonded to one Ni(1), one Al(1), one Al(2), and one Al(3) atom to form a mixture of distorted corner and edge-sharing OAl3Ni trigonal pyramids. In the eighth O site, O(8) is bonded to one Ni(1), one Al(1), one Al(2), and one Al(4) atom to form a mixture of distorted corner and edge-sharing OAl3Ni trigonal pyramids.