CaCoO2 crystallizes in the monoclinic P2_1/m space group. There are two inequivalent Ca sites. In the first Ca site, Ca(1) is bonded to one O(4), two equivalent O(3), and three equivalent O(1) atoms to form distorted CaO6 octahedra that share corners with four equivalent Ca(2)O6 pentagonal pyramids,  a cornercorner with one Co(2)O4 tetrahedra, corners with two equivalent Co(1)O4 trigonal pyramids, edges with four equivalent Ca(1)O6 octahedra,  an edgeedge with one Ca(2)O6 pentagonal pyramid, edges with two equivalent Co(2)O4 tetrahedra, and edges with three equivalent Co(1)O4 trigonal pyramids. In the second Ca site, Ca(2) is bonded to two equivalent O(2), two equivalent O(3), and two equivalent O(4) atoms to form distorted CaO6 pentagonal pyramids that share corners with four equivalent Ca(1)O6 octahedra, corners with four equivalent Co(2)O4 tetrahedra,  an edgeedge with one Ca(1)O6 octahedra,  an edgeedge with one Co(2)O4 tetrahedra, edges with two equivalent Co(1)O4 trigonal pyramids, and faces with two equivalent Ca(2)O6 pentagonal pyramids. The corner-sharing octahedral tilt angles range from 5-72°. There are two inequivalent Co sites. In the first Co site, Co(1) is bonded to one O(2), one O(3), and two equivalent O(1) atoms to form CoO4 trigonal pyramids that share corners with two equivalent Ca(1)O6 octahedra, corners with three equivalent Co(2)O4 tetrahedra, corners with two equivalent Co(1)O4 trigonal pyramids, edges with three equivalent Ca(1)O6 octahedra, and edges with two equivalent Ca(2)O6 pentagonal pyramids. The corner-sharing octahedral tilt angles are 13°. In the second Co site, Co(2) is bonded to one O(1), one O(2), and two equivalent O(4) atoms to form CoO4 tetrahedra that share  a cornercorner with one Ca(1)O6 octahedra, corners with four equivalent Ca(2)O6 pentagonal pyramids, corners with two equivalent Co(2)O4 tetrahedra, corners with three equivalent Co(1)O4 trigonal pyramids, edges with two equivalent Ca(1)O6 octahedra, and  an edgeedge with one Ca(2)O6 pentagonal pyramid. The corner-sharing octahedral tilt angles are 1°. There are four inequivalent O sites. In the first O site, O(1) is bonded to three equivalent Ca(1), one Co(2), and two equivalent Co(1) atoms to form distorted OCa3Co3 octahedra that share  a cornercorner with one O(4)Ca3Co2 square pyramid, corners with two equivalent O(3)Ca4Co square pyramids, edges with four equivalent O(1)Ca3Co3 octahedra, edges with two equivalent O(4)Ca3Co2 square pyramids, and edges with three equivalent O(3)Ca4Co square pyramids. In the second O site, O(2) is bonded in a rectangular see-saw-like geometry to two equivalent Ca(2), one Co(1), and one Co(2) atom. In the third O site, O(3) is bonded to two equivalent Ca(1), two equivalent Ca(2), and one Co(1) atom to form OCa4Co square pyramids that share corners with two equivalent O(1)Ca3Co3 octahedra, corners with four equivalent O(4)Ca3Co2 square pyramids, edges with three equivalent O(1)Ca3Co3 octahedra,  an edgeedge with one O(4)Ca3Co2 square pyramid, and edges with two equivalent O(3)Ca4Co square pyramids. The corner-sharing octahedral tilt angles are 15°. In the fourth O site, O(4) is bonded to one Ca(1), two equivalent Ca(2), and two equivalent Co(2) atoms to form distorted OCa3Co2 square pyramids that share  a cornercorner with one O(1)Ca3Co3 octahedra, corners with four equivalent O(3)Ca4Co square pyramids, edges with two equivalent O(1)Ca3Co3 octahedra,  an edgeedge with one O(3)Ca4Co square pyramid, and edges with two equivalent O(4)Ca3Co2 square pyramids. The corner-sharing octahedral tilt angles are 16°.
CaCoO2 crystallizes in the monoclinic P2_1/m space group. There are two inequivalent Ca sites. In the first Ca site, Ca(1) is bonded to one O(4), two equivalent O(3), and three equivalent O(1) atoms to form distorted CaO6 octahedra that share corners with four equivalent Ca(2)O6 pentagonal pyramids,  a cornercorner with one Co(2)O4 tetrahedra, corners with two equivalent Co(1)O4 trigonal pyramids, edges with four equivalent Ca(1)O6 octahedra,  an edgeedge with one Ca(2)O6 pentagonal pyramid, edges with two equivalent Co(2)O4 tetrahedra, and edges with three equivalent Co(1)O4 trigonal pyramids. The Ca(1)-O(4) bond length is 2.34 Å. Both Ca(1)-O(3) bond lengths are 2.25 Å. There are two shorter (2.49 Å) and one longer (2.70 Å) Ca(1)-O(1) bond length. In the second Ca site, Ca(2) is bonded to two equivalent O(2), two equivalent O(3), and two equivalent O(4) atoms to form distorted CaO6 pentagonal pyramids that share corners with four equivalent Ca(1)O6 octahedra, corners with four equivalent Co(2)O4 tetrahedra,  an edgeedge with one Ca(1)O6 octahedra,  an edgeedge with one Co(2)O4 tetrahedra, edges with two equivalent Co(1)O4 trigonal pyramids, and faces with two equivalent Ca(2)O6 pentagonal pyramids. The corner-sharing octahedral tilt angles range from 5-72°. Both Ca(2)-O(2) bond lengths are 2.38 Å. Both Ca(2)-O(3) bond lengths are 2.47 Å. Both Ca(2)-O(4) bond lengths are 2.45 Å. There are two inequivalent Co sites. In the first Co site, Co(1) is bonded to one O(2), one O(3), and two equivalent O(1) atoms to form CoO4 trigonal pyramids that share corners with two equivalent Ca(1)O6 octahedra, corners with three equivalent Co(2)O4 tetrahedra, corners with two equivalent Co(1)O4 trigonal pyramids, edges with three equivalent Ca(1)O6 octahedra, and edges with two equivalent Ca(2)O6 pentagonal pyramids. The corner-sharing octahedral tilt angles are 13°. The Co(1)-O(2) bond length is 1.91 Å. The Co(1)-O(3) bond length is 2.03 Å. Both Co(1)-O(1) bond lengths are 2.06 Å. In the second Co site, Co(2) is bonded to one O(1), one O(2), and two equivalent O(4) atoms to form CoO4 tetrahedra that share  a cornercorner with one Ca(1)O6 octahedra, corners with four equivalent Ca(2)O6 pentagonal pyramids, corners with two equivalent Co(2)O4 tetrahedra, corners with three equivalent Co(1)O4 trigonal pyramids, edges with two equivalent Ca(1)O6 octahedra, and  an edgeedge with one Ca(2)O6 pentagonal pyramid. The corner-sharing octahedral tilt angles are 1°. The Co(2)-O(1) bond length is 2.08 Å. The Co(2)-O(2) bond length is 1.87 Å. Both Co(2)-O(4) bond lengths are 2.05 Å. There are four inequivalent O sites. In the first O site, O(1) is bonded to three equivalent Ca(1), one Co(2), and two equivalent Co(1) atoms to form distorted OCa3Co3 octahedra that share  a cornercorner with one O(4)Ca3Co2 square pyramid, corners with two equivalent O(3)Ca4Co square pyramids, edges with four equivalent O(1)Ca3Co3 octahedra, edges with two equivalent O(4)Ca3Co2 square pyramids, and edges with three equivalent O(3)Ca4Co square pyramids. In the second O site, O(2) is bonded in a rectangular see-saw-like geometry to two equivalent Ca(2), one Co(1), and one Co(2) atom. In the third O site, O(3) is bonded to two equivalent Ca(1), two equivalent Ca(2), and one Co(1) atom to form OCa4Co square pyramids that share corners with two equivalent O(1)Ca3Co3 octahedra, corners with four equivalent O(4)Ca3Co2 square pyramids, edges with three equivalent O(1)Ca3Co3 octahedra,  an edgeedge with one O(4)Ca3Co2 square pyramid, and edges with two equivalent O(3)Ca4Co square pyramids. The corner-sharing octahedral tilt angles are 15°. In the fourth O site, O(4) is bonded to one Ca(1), two equivalent Ca(2), and two equivalent Co(2) atoms to form distorted OCa3Co2 square pyramids that share  a cornercorner with one O(1)Ca3Co3 octahedra, corners with four equivalent O(3)Ca4Co square pyramids, edges with two equivalent O(1)Ca3Co3 octahedra,  an edgeedge with one O(3)Ca4Co square pyramid, and edges with two equivalent O(4)Ca3Co2 square pyramids. The corner-sharing octahedral tilt angles are 16°.