CaCo2O4 crystallizes in the monoclinic C2/m space group. Ca(1) is bonded in a 6-coordinate geometry to one O(1), one O(2), two equivalent O(3), and two equivalent O(4) atoms. There are two inequivalent Co sites. In the first Co site, Co(1) is bonded to one O(2), two equivalent O(1), and three equivalent O(3) atoms to form a mixture of distorted edge and corner-sharing CoO6 octahedra. The corner-sharing octahedral tilt angles range from 51-60°. In the second Co site, Co(2) is bonded to one O(1), two equivalent O(2), and three equivalent O(4) atoms to form a mixture of distorted edge and corner-sharing CoO6 octahedra. The corner-sharing octahedral tilt angles range from 51-60°. There are four inequivalent O sites. In the first O site, O(1) is bonded to one Ca(1), one Co(2), and two equivalent Co(1) atoms to form OCaCo3 trigonal pyramids that share corners with two equivalent O(3)Ca2Co3 square pyramids,  a cornercorner with one O(4)Ca2Co3 trigonal bipyramid, corners with two equivalent O(1)CaCo3 trigonal pyramids, corners with five equivalent O(2)CaCo3 trigonal pyramids, edges with three equivalent O(3)Ca2Co3 square pyramids, and edges with two equivalent O(4)Ca2Co3 trigonal bipyramids. In the second O site, O(2) is bonded to one Ca(1), one Co(1), and two equivalent Co(2) atoms to form distorted OCaCo3 trigonal pyramids that share corners with five equivalent O(3)Ca2Co3 square pyramids, corners with two equivalent O(4)Ca2Co3 trigonal bipyramids, corners with two equivalent O(2)CaCo3 trigonal pyramids, corners with five equivalent O(1)CaCo3 trigonal pyramids, and edges with three equivalent O(4)Ca2Co3 trigonal bipyramids. In the third O site, O(3) is bonded to two equivalent Ca(1) and three equivalent Co(1) atoms to form OCa2Co3 square pyramids that share corners with two equivalent O(4)Ca2Co3 trigonal bipyramids, corners with two equivalent O(1)CaCo3 trigonal pyramids, corners with five equivalent O(2)CaCo3 trigonal pyramids, edges with four equivalent O(3)Ca2Co3 square pyramids,  an edgeedge with one O(4)Ca2Co3 trigonal bipyramid, and edges with three equivalent O(1)CaCo3 trigonal pyramids. In the fourth O site, O(4) is bonded to two equivalent Ca(1) and three equivalent Co(2) atoms to form distorted OCa2Co3 trigonal bipyramids that share corners with two equivalent O(3)Ca2Co3 square pyramids,  a cornercorner with one O(1)CaCo3 trigonal pyramid, corners with two equivalent O(2)CaCo3 trigonal pyramids,  an edgeedge with one O(3)Ca2Co3 square pyramid, edges with four equivalent O(4)Ca2Co3 trigonal bipyramids, edges with two equivalent O(1)CaCo3 trigonal pyramids, and edges with three equivalent O(2)CaCo3 trigonal pyramids.
CaCo2O4 crystallizes in the monoclinic C2/m space group. Ca(1) is bonded in a 6-coordinate geometry to one O(1), one O(2), two equivalent O(3), and two equivalent O(4) atoms. The Ca(1)-O(1) bond length is 2.37 Å. The Ca(1)-O(2) bond length is 2.50 Å. Both Ca(1)-O(3) bond lengths are 2.29 Å. Both Ca(1)-O(4) bond lengths are 2.24 Å. There are two inequivalent Co sites. In the first Co site, Co(1) is bonded to one O(2), two equivalent O(1), and three equivalent O(3) atoms to form a mixture of distorted edge and corner-sharing CoO6 octahedra. The corner-sharing octahedral tilt angles range from 51-60°. The Co(1)-O(2) bond length is 1.89 Å. Both Co(1)-O(1) bond lengths are 2.02 Å. There are two shorter (2.12 Å) and one longer (2.40 Å) Co(1)-O(3) bond length. In the second Co site, Co(2) is bonded to one O(1), two equivalent O(2), and three equivalent O(4) atoms to form a mixture of distorted edge and corner-sharing CoO6 octahedra. The corner-sharing octahedral tilt angles range from 51-60°. The Co(2)-O(1) bond length is 1.94 Å. Both Co(2)-O(2) bond lengths are 2.06 Å. There is one shorter (1.94 Å) and two longer (2.15 Å) Co(2)-O(4) bond lengths. There are four inequivalent O sites. In the first O site, O(1) is bonded to one Ca(1), one Co(2), and two equivalent Co(1) atoms to form OCaCo3 trigonal pyramids that share corners with two equivalent O(3)Ca2Co3 square pyramids,  a cornercorner with one O(4)Ca2Co3 trigonal bipyramid, corners with two equivalent O(1)CaCo3 trigonal pyramids, corners with five equivalent O(2)CaCo3 trigonal pyramids, edges with three equivalent O(3)Ca2Co3 square pyramids, and edges with two equivalent O(4)Ca2Co3 trigonal bipyramids. In the second O site, O(2) is bonded to one Ca(1), one Co(1), and two equivalent Co(2) atoms to form distorted OCaCo3 trigonal pyramids that share corners with five equivalent O(3)Ca2Co3 square pyramids, corners with two equivalent O(4)Ca2Co3 trigonal bipyramids, corners with two equivalent O(2)CaCo3 trigonal pyramids, corners with five equivalent O(1)CaCo3 trigonal pyramids, and edges with three equivalent O(4)Ca2Co3 trigonal bipyramids. In the third O site, O(3) is bonded to two equivalent Ca(1) and three equivalent Co(1) atoms to form OCa2Co3 square pyramids that share corners with two equivalent O(4)Ca2Co3 trigonal bipyramids, corners with two equivalent O(1)CaCo3 trigonal pyramids, corners with five equivalent O(2)CaCo3 trigonal pyramids, edges with four equivalent O(3)Ca2Co3 square pyramids,  an edgeedge with one O(4)Ca2Co3 trigonal bipyramid, and edges with three equivalent O(1)CaCo3 trigonal pyramids. In the fourth O site, O(4) is bonded to two equivalent Ca(1) and three equivalent Co(2) atoms to form distorted OCa2Co3 trigonal bipyramids that share corners with two equivalent O(3)Ca2Co3 square pyramids,  a cornercorner with one O(1)CaCo3 trigonal pyramid, corners with two equivalent O(2)CaCo3 trigonal pyramids,  an edgeedge with one O(3)Ca2Co3 square pyramid, edges with four equivalent O(4)Ca2Co3 trigonal bipyramids, edges with two equivalent O(1)CaCo3 trigonal pyramids, and edges with three equivalent O(2)CaCo3 trigonal pyramids.