Co2AlO4 crystallizes in the triclinic P-1 space group. There are four inequivalent Co sites. In the first Co site, Co(1) is bonded in a square co-planar geometry to two equivalent O(2) and two equivalent O(3) atoms. In the second Co site, Co(2) is bonded in a square co-planar geometry to two equivalent O(1) and two equivalent O(4) atoms. In the third Co site, Co(3) is bonded in a square co-planar geometry to two equivalent O(2) and two equivalent O(4) atoms. In the fourth Co site, Co(4) is bonded in a square co-planar geometry to two equivalent O(1) and two equivalent O(3) atoms. Al(1) is bonded to one O(3), one O(4), two equivalent O(1), and two equivalent O(2) atoms to form edge-sharing AlO6 pentagonal pyramids. There are four inequivalent O sites. In the first O site, O(1) is bonded to one Co(2), one Co(4), and two equivalent Al(1) atoms to form a mixture of edge and corner-sharing OAl2Co2 tetrahedra. In the second O site, O(2) is bonded to one Co(1), one Co(3), and two equivalent Al(1) atoms to form a mixture of distorted edge and corner-sharing OAl2Co2 tetrahedra. In the third O site, O(3) is bonded in a trigonal non-coplanar geometry to one Co(1), one Co(4), and one Al(1) atom. In the fourth O site, O(4) is bonded in a trigonal non-coplanar geometry to one Co(2), one Co(3), and one Al(1) atom.
Co2AlO4 crystallizes in the triclinic P-1 space group. There are four inequivalent Co sites. In the first Co site, Co(1) is bonded in a square co-planar geometry to two equivalent O(2) and two equivalent O(3) atoms. Both Co(1)-O(2) bond lengths are 1.88 Å. Both Co(1)-O(3) bond lengths are 1.87 Å. In the second Co site, Co(2) is bonded in a square co-planar geometry to two equivalent O(1) and two equivalent O(4) atoms. Both Co(2)-O(1) bond lengths are 1.87 Å. Both Co(2)-O(4) bond lengths are 1.89 Å. In the third Co site, Co(3) is bonded in a square co-planar geometry to two equivalent O(2) and two equivalent O(4) atoms. Both Co(3)-O(2) bond lengths are 1.95 Å. Both Co(3)-O(4) bond lengths are 1.83 Å. In the fourth Co site, Co(4) is bonded in a square co-planar geometry to two equivalent O(1) and two equivalent O(3) atoms. Both Co(4)-O(1) bond lengths are 1.95 Å. Both Co(4)-O(3) bond lengths are 1.87 Å. Al(1) is bonded to one O(3), one O(4), two equivalent O(1), and two equivalent O(2) atoms to form edge-sharing AlO6 pentagonal pyramids. The Al(1)-O(3) bond length is 1.92 Å. The Al(1)-O(4) bond length is 1.92 Å. There is one shorter (1.93 Å) and one longer (2.04 Å) Al(1)-O(1) bond length. There is one shorter (1.94 Å) and one longer (2.07 Å) Al(1)-O(2) bond length. There are four inequivalent O sites. In the first O site, O(1) is bonded to one Co(2), one Co(4), and two equivalent Al(1) atoms to form a mixture of edge and corner-sharing OAl2Co2 tetrahedra. In the second O site, O(2) is bonded to one Co(1), one Co(3), and two equivalent Al(1) atoms to form a mixture of distorted edge and corner-sharing OAl2Co2 tetrahedra. In the third O site, O(3) is bonded in a trigonal non-coplanar geometry to one Co(1), one Co(4), and one Al(1) atom. In the fourth O site, O(4) is bonded in a trigonal non-coplanar geometry to one Co(2), one Co(3), and one Al(1) atom.