Co2AlO4 is Spinel-like structured and crystallizes in the orthorhombic Imma space group. There are two inequivalent Co sites. In the first Co site, Co(1) is bonded to two equivalent O(1) and four equivalent O(2) atoms to form CoO6 octahedra that share corners with six equivalent Co(2)O4 tetrahedra, edges with two equivalent Co(1)O6 octahedra, and edges with four equivalent Al(1)O6 octahedra. In the second Co site, Co(2) is bonded to two equivalent O(1) and two equivalent O(2) atoms to form CoO4 tetrahedra that share corners with six equivalent Co(1)O6 octahedra and corners with six equivalent Al(1)O6 octahedra. The corner-sharing octahedral tilt angles range from 55-63°. Al(1) is bonded to two equivalent O(2) and four equivalent O(1) atoms to form AlO6 octahedra that share corners with six equivalent Co(2)O4 tetrahedra, edges with two equivalent Al(1)O6 octahedra, and edges with four equivalent Co(1)O6 octahedra. There are two inequivalent O sites. In the first O site, O(1) is bonded to one Co(1), one Co(2), and two equivalent Al(1) atoms to form a mixture of distorted edge and corner-sharing OAl2Co2 trigonal pyramids. In the second O site, O(2) is bonded in a rectangular see-saw-like geometry to one Co(2), two equivalent Co(1), and one Al(1) atom.
Co2AlO4 is Spinel-like structured and crystallizes in the orthorhombic Imma space group. There are two inequivalent Co sites. In the first Co site, Co(1) is bonded to two equivalent O(1) and four equivalent O(2) atoms to form CoO6 octahedra that share corners with six equivalent Co(2)O4 tetrahedra, edges with two equivalent Co(1)O6 octahedra, and edges with four equivalent Al(1)O6 octahedra. Both Co(1)-O(1) bond lengths are 1.95 Å. All Co(1)-O(2) bond lengths are 2.02 Å. In the second Co site, Co(2) is bonded to two equivalent O(1) and two equivalent O(2) atoms to form CoO4 tetrahedra that share corners with six equivalent Co(1)O6 octahedra and corners with six equivalent Al(1)O6 octahedra. The corner-sharing octahedral tilt angles range from 55-63°. Both Co(2)-O(1) bond lengths are 1.99 Å. Both Co(2)-O(2) bond lengths are 1.96 Å. Al(1) is bonded to two equivalent O(2) and four equivalent O(1) atoms to form AlO6 octahedra that share corners with six equivalent Co(2)O4 tetrahedra, edges with two equivalent Al(1)O6 octahedra, and edges with four equivalent Co(1)O6 octahedra. Both Al(1)-O(2) bond lengths are 1.88 Å. All Al(1)-O(1) bond lengths are 1.95 Å. There are two inequivalent O sites. In the first O site, O(1) is bonded to one Co(1), one Co(2), and two equivalent Al(1) atoms to form a mixture of distorted edge and corner-sharing OAl2Co2 trigonal pyramids. In the second O site, O(2) is bonded in a rectangular see-saw-like geometry to one Co(2), two equivalent Co(1), and one Al(1) atom.