CaCuO2 crystallizes in the triclinic P1 space group. There are four inequivalent Ca sites. In the first Ca site, Ca(1) is bonded to one O(4), one O(8), two equivalent O(6), and two equivalent O(7) atoms to form a mixture of corner and edge-sharing CaO6 octahedra. The corner-sharing octahedral tilt angles are 11°. In the second Ca site, Ca(2) is bonded to one O(1), one O(6), two equivalent O(5), and two equivalent O(8) atoms to form a mixture of corner and edge-sharing CaO6 octahedra. The corner-sharing octahedral tilt angles are 10°. In the third Ca site, Ca(3) is bonded to one O(2), one O(7), two equivalent O(3), and two equivalent O(8) atoms to form a mixture of corner and edge-sharing CaO6 octahedra. The corner-sharing octahedral tilt angles are 10°. In the fourth Ca site, Ca(4) is bonded to one O(3), one O(5), two equivalent O(2), and two equivalent O(6) atoms to form a mixture of corner and edge-sharing CaO6 octahedra. The corner-sharing octahedral tilt angles are 11°. There are four inequivalent Cu sites. In the first Cu site, Cu(1) is bonded in a square co-planar geometry to two equivalent O(4) and two equivalent O(5) atoms. In the second Cu site, Cu(2) is bonded in a 5-coordinate geometry to one O(6), two equivalent O(3), and two equivalent O(4) atoms. In the third Cu site, Cu(3) is bonded in a 3-coordinate geometry to one O(1), one O(8), and two equivalent O(2) atoms. In the fourth Cu site, Cu(4) is bonded in a square co-planar geometry to two equivalent O(1) and two equivalent O(7) atoms. There are eight inequivalent O sites. In the first O site, O(1) is bonded in a 4-coordinate geometry to one Ca(2), one Cu(3), and two equivalent Cu(4) atoms. In the second O site, O(2) is bonded to one Ca(3), two equivalent Ca(4), and two equivalent Cu(3) atoms to form OCa3Cu2 square pyramids that share corners with two equivalent O(6)Ca5Cu octahedra,  a cornercorner with one O(7)Ca3Cu2 square pyramid, corners with two equivalent O(5)Ca3Cu2 square pyramids,  an edgeedge with one O(6)Ca5Cu octahedra, edges with two equivalent O(8)Ca5Cu octahedra, edges with two equivalent O(2)Ca3Cu2 square pyramids, and edges with two equivalent O(3)Ca3Cu2 square pyramids. The corner-sharing octahedral tilt angles are 8°. In the third O site, O(3) is bonded to one Ca(4), two equivalent Ca(3), and two equivalent Cu(2) atoms to form OCa3Cu2 square pyramids that share corners with two equivalent O(8)Ca5Cu octahedra,  a cornercorner with one O(5)Ca3Cu2 square pyramid, corners with two equivalent O(7)Ca3Cu2 square pyramids,  an edgeedge with one O(8)Ca5Cu octahedra, edges with two equivalent O(6)Ca5Cu octahedra, edges with two equivalent O(2)Ca3Cu2 square pyramids, and edges with two equivalent O(3)Ca3Cu2 square pyramids. The corner-sharing octahedral tilt angles range from 8-9°. In the fourth O site, O(4) is bonded in a 4-coordinate geometry to one Ca(1), two equivalent Cu(1), and two equivalent Cu(2) atoms. In the fifth O site, O(5) is bonded to one Ca(4), two equivalent Ca(2), and two equivalent Cu(1) atoms to form distorted OCa3Cu2 square pyramids that share corners with two equivalent O(8)Ca5Cu octahedra,  a cornercorner with one O(3)Ca3Cu2 square pyramid, corners with two equivalent O(2)Ca3Cu2 square pyramids,  an edgeedge with one O(8)Ca5Cu octahedra, edges with two equivalent O(6)Ca5Cu octahedra, and edges with two equivalent O(5)Ca3Cu2 square pyramids. The corner-sharing octahedral tilt angles are 11°. In the sixth O site, O(6) is bonded to one Ca(2), two equivalent Ca(1), two equivalent Ca(4), and one Cu(2) atom to form OCa5Cu octahedra that share corners with two equivalent O(2)Ca3Cu2 square pyramids, corners with two equivalent O(7)Ca3Cu2 square pyramids, edges with two equivalent O(6)Ca5Cu octahedra, edges with two equivalent O(8)Ca5Cu octahedra,  an edgeedge with one O(2)Ca3Cu2 square pyramid,  an edgeedge with one O(7)Ca3Cu2 square pyramid, edges with two equivalent O(3)Ca3Cu2 square pyramids, and edges with two equivalent O(5)Ca3Cu2 square pyramids. In the seventh O site, O(7) is bonded to one Ca(3), two equivalent Ca(1), and two equivalent Cu(4) atoms to form distorted OCa3Cu2 square pyramids that share corners with two equivalent O(6)Ca5Cu octahedra,  a cornercorner with one O(2)Ca3Cu2 square pyramid, corners with two equivalent O(3)Ca3Cu2 square pyramids,  an edgeedge with one O(6)Ca5Cu octahedra, edges with two equivalent O(8)Ca5Cu octahedra, and edges with two equivalent O(7)Ca3Cu2 square pyramids. The corner-sharing octahedral tilt angles are 11°. In the eighth O site, O(8) is bonded to one Ca(1), two equivalent Ca(2), two equivalent Ca(3), and one Cu(3) atom to form OCa5Cu octahedra that share corners with two equivalent O(3)Ca3Cu2 square pyramids, corners with two equivalent O(5)Ca3Cu2 square pyramids, edges with two equivalent O(6)Ca5Cu octahedra, edges with two equivalent O(8)Ca5Cu octahedra,  an edgeedge with one O(3)Ca3Cu2 square pyramid,  an edgeedge with one O(5)Ca3Cu2 square pyramid, edges with two equivalent O(2)Ca3Cu2 square pyramids, and edges with two equivalent O(7)Ca3Cu2 square pyramids.
CaCuO2 crystallizes in the triclinic P1 space group. There are four inequivalent Ca sites. In the first Ca site, Ca(1) is bonded to one O(4), one O(8), two equivalent O(6), and two equivalent O(7) atoms to form a mixture of corner and edge-sharing CaO6 octahedra. The corner-sharing octahedral tilt angles are 11°. The Ca(1)-O(4) bond length is 2.42 Å. The Ca(1)-O(8) bond length is 2.40 Å. Both Ca(1)-O(6) bond lengths are 2.28 Å. There is one shorter (2.40 Å) and one longer (2.42 Å) Ca(1)-O(7) bond length. In the second Ca site, Ca(2) is bonded to one O(1), one O(6), two equivalent O(5), and two equivalent O(8) atoms to form a mixture of corner and edge-sharing CaO6 octahedra. The corner-sharing octahedral tilt angles are 10°. The Ca(2)-O(1) bond length is 2.42 Å. The Ca(2)-O(6) bond length is 2.40 Å. There is one shorter (2.39 Å) and one longer (2.43 Å) Ca(2)-O(5) bond length. Both Ca(2)-O(8) bond lengths are 2.28 Å. In the third Ca site, Ca(3) is bonded to one O(2), one O(7), two equivalent O(3), and two equivalent O(8) atoms to form a mixture of corner and edge-sharing CaO6 octahedra. The corner-sharing octahedral tilt angles are 10°. The Ca(3)-O(2) bond length is 2.45 Å. The Ca(3)-O(7) bond length is 2.38 Å. There is one shorter (2.34 Å) and one longer (2.37 Å) Ca(3)-O(3) bond length. There is one shorter (2.29 Å) and one longer (2.32 Å) Ca(3)-O(8) bond length. In the fourth Ca site, Ca(4) is bonded to one O(3), one O(5), two equivalent O(2), and two equivalent O(6) atoms to form a mixture of corner and edge-sharing CaO6 octahedra. The corner-sharing octahedral tilt angles are 11°. The Ca(4)-O(3) bond length is 2.45 Å. The Ca(4)-O(5) bond length is 2.38 Å. There is one shorter (2.34 Å) and one longer (2.36 Å) Ca(4)-O(2) bond length. There is one shorter (2.29 Å) and one longer (2.31 Å) Ca(4)-O(6) bond length. There are four inequivalent Cu sites. In the first Cu site, Cu(1) is bonded in a square co-planar geometry to two equivalent O(4) and two equivalent O(5) atoms. There is one shorter (1.99 Å) and one longer (2.01 Å) Cu(1)-O(4) bond length. There is one shorter (1.98 Å) and one longer (1.99 Å) Cu(1)-O(5) bond length. In the second Cu site, Cu(2) is bonded in a 5-coordinate geometry to one O(6), two equivalent O(3), and two equivalent O(4) atoms. The Cu(2)-O(6) bond length is 2.55 Å. There is one shorter (1.90 Å) and one longer (2.04 Å) Cu(2)-O(3) bond length. There is one shorter (1.90 Å) and one longer (2.64 Å) Cu(2)-O(4) bond length. In the third Cu site, Cu(3) is bonded in a 3-coordinate geometry to one O(1), one O(8), and two equivalent O(2) atoms. The Cu(3)-O(1) bond length is 1.90 Å. The Cu(3)-O(8) bond length is 2.54 Å. There is one shorter (1.90 Å) and one longer (2.04 Å) Cu(3)-O(2) bond length. In the fourth Cu site, Cu(4) is bonded in a square co-planar geometry to two equivalent O(1) and two equivalent O(7) atoms. There is one shorter (1.99 Å) and one longer (2.01 Å) Cu(4)-O(1) bond length. There is one shorter (1.98 Å) and one longer (1.99 Å) Cu(4)-O(7) bond length. There are eight inequivalent O sites. In the first O site, O(1) is bonded in a 4-coordinate geometry to one Ca(2), one Cu(3), and two equivalent Cu(4) atoms. In the second O site, O(2) is bonded to one Ca(3), two equivalent Ca(4), and two equivalent Cu(3) atoms to form OCa3Cu2 square pyramids that share corners with two equivalent O(6)Ca5Cu octahedra,  a cornercorner with one O(7)Ca3Cu2 square pyramid, corners with two equivalent O(5)Ca3Cu2 square pyramids,  an edgeedge with one O(6)Ca5Cu octahedra, edges with two equivalent O(8)Ca5Cu octahedra, edges with two equivalent O(2)Ca3Cu2 square pyramids, and edges with two equivalent O(3)Ca3Cu2 square pyramids. The corner-sharing octahedral tilt angles are 8°. In the third O site, O(3) is bonded to one Ca(4), two equivalent Ca(3), and two equivalent Cu(2) atoms to form OCa3Cu2 square pyramids that share corners with two equivalent O(8)Ca5Cu octahedra,  a cornercorner with one O(5)Ca3Cu2 square pyramid, corners with two equivalent O(7)Ca3Cu2 square pyramids,  an edgeedge with one O(8)Ca5Cu octahedra, edges with two equivalent O(6)Ca5Cu octahedra, edges with two equivalent O(2)Ca3Cu2 square pyramids, and edges with two equivalent O(3)Ca3Cu2 square pyramids. The corner-sharing octahedral tilt angles range from 8-9°. In the fourth O site, O(4) is bonded in a 4-coordinate geometry to one Ca(1), two equivalent Cu(1), and two equivalent Cu(2) atoms. In the fifth O site, O(5) is bonded to one Ca(4), two equivalent Ca(2), and two equivalent Cu(1) atoms to form distorted OCa3Cu2 square pyramids that share corners with two equivalent O(8)Ca5Cu octahedra,  a cornercorner with one O(3)Ca3Cu2 square pyramid, corners with two equivalent O(2)Ca3Cu2 square pyramids,  an edgeedge with one O(8)Ca5Cu octahedra, edges with two equivalent O(6)Ca5Cu octahedra, and edges with two equivalent O(5)Ca3Cu2 square pyramids. The corner-sharing octahedral tilt angles are 11°. In the sixth O site, O(6) is bonded to one Ca(2), two equivalent Ca(1), two equivalent Ca(4), and one Cu(2) atom to form OCa5Cu octahedra that share corners with two equivalent O(2)Ca3Cu2 square pyramids, corners with two equivalent O(7)Ca3Cu2 square pyramids, edges with two equivalent O(6)Ca5Cu octahedra, edges with two equivalent O(8)Ca5Cu octahedra,  an edgeedge with one O(2)Ca3Cu2 square pyramid,  an edgeedge with one O(7)Ca3Cu2 square pyramid, edges with two equivalent O(3)Ca3Cu2 square pyramids, and edges with two equivalent O(5)Ca3Cu2 square pyramids. In the seventh O site, O(7) is bonded to one Ca(3), two equivalent Ca(1), and two equivalent Cu(4) atoms to form distorted OCa3Cu2 square pyramids that share corners with two equivalent O(6)Ca5Cu octahedra,  a cornercorner with one O(2)Ca3Cu2 square pyramid, corners with two equivalent O(3)Ca3Cu2 square pyramids,  an edgeedge with one O(6)Ca5Cu octahedra, edges with two equivalent O(8)Ca5Cu octahedra, and edges with two equivalent O(7)Ca3Cu2 square pyramids. The corner-sharing octahedral tilt angles are 11°. In the eighth O site, O(8) is bonded to one Ca(1), two equivalent Ca(2), two equivalent Ca(3), and one Cu(3) atom to form OCa5Cu octahedra that share corners with two equivalent O(3)Ca3Cu2 square pyramids, corners with two equivalent O(5)Ca3Cu2 square pyramids, edges with two equivalent O(6)Ca5Cu octahedra, edges with two equivalent O(8)Ca5Cu octahedra,  an edgeedge with one O(3)Ca3Cu2 square pyramid,  an edgeedge with one O(5)Ca3Cu2 square pyramid, edges with two equivalent O(2)Ca3Cu2 square pyramids, and edges with two equivalent O(7)Ca3Cu2 square pyramids.