Ca5(CuO2)6 crystallizes in the monoclinic P2/c space group. There are three inequivalent Ca sites. In the first Ca site, Ca(1) is bonded to one O(1), one O(5), two equivalent O(2), and two equivalent O(4) atoms to form edge-sharing CaO6 octahedra. In the second Ca site, Ca(2) is bonded to one O(1), one O(2), one O(3), one O(4), one O(5), and one O(6) atom to form distorted edge-sharing CaO6 octahedra. In the third Ca site, Ca(3) is bonded in a 8-coordinate geometry to two equivalent O(1), two equivalent O(3), two equivalent O(5), and two equivalent O(6) atoms. 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(1) and two equivalent O(2) atoms. In the second Cu site, Cu(2) is bonded in a rectangular see-saw-like geometry to one O(1), one O(2), and two equivalent O(3) atoms. In the third Cu site, Cu(3) is bonded in a rectangular see-saw-like geometry to one O(5), one O(6), and two equivalent O(4) atoms. In the fourth Cu site, Cu(4) is bonded in a square co-planar geometry to two equivalent O(5) and two equivalent O(6) atoms. There are six inequivalent O sites. In the first O site, O(4) is bonded to one Ca(2), two equivalent Ca(1), and two equivalent Cu(3) atoms to form distorted OCa3Cu2 square pyramids that share corners with three equivalent O(2)Ca3Cu2 trigonal bipyramids,  a cornercorner with one O(3)Ca2Cu2 trigonal pyramid, edges with two equivalent O(4)Ca3Cu2 square pyramids, and  an edgeedge with one O(2)Ca3Cu2 trigonal bipyramid. In the second O site, O(5) is bonded in a 5-coordinate geometry to one Ca(1), one Ca(2), one Ca(3), one Cu(3), and one Cu(4) atom. In the third O site, O(6) is bonded in a distorted see-saw-like geometry to one Ca(2), one Ca(3), one Cu(3), and one Cu(4) atom. In the fourth O site, O(1) is bonded in a 5-coordinate geometry to one Ca(1), one Ca(2), one Ca(3), one Cu(1), and one Cu(2) atom. In the fifth O site, O(2) is bonded to one Ca(2), two equivalent Ca(1), one Cu(1), and one Cu(2) atom to form distorted OCa3Cu2 trigonal bipyramids that share corners with three equivalent O(4)Ca3Cu2 square pyramids,  a cornercorner with one O(2)Ca3Cu2 trigonal bipyramid,  a cornercorner with one O(3)Ca2Cu2 trigonal pyramid,  an edgeedge with one O(4)Ca3Cu2 square pyramid,  an edgeedge with one O(2)Ca3Cu2 trigonal bipyramid, and  an edgeedge with one O(3)Ca2Cu2 trigonal pyramid. In the sixth O site, O(3) is bonded to one Ca(2), one Ca(3), and two equivalent Cu(2) atoms to form distorted OCa2Cu2 trigonal pyramids that share  a cornercorner with one O(4)Ca3Cu2 square pyramid,  a cornercorner with one O(2)Ca3Cu2 trigonal bipyramid,  a cornercorner with one O(3)Ca2Cu2 trigonal pyramid,  an edgeedge with one O(2)Ca3Cu2 trigonal bipyramid, and  an edgeedge with one O(3)Ca2Cu2 trigonal pyramid.
Ca5(CuO2)6 crystallizes in the monoclinic P2/c space group. There are three inequivalent Ca sites. In the first Ca site, Ca(1) is bonded to one O(1), one O(5), two equivalent O(2), and two equivalent O(4) atoms to form edge-sharing CaO6 octahedra. The Ca(1)-O(1) bond length is 2.35 Å. The Ca(1)-O(5) bond length is 2.35 Å. There is one shorter (2.38 Å) and one longer (2.39 Å) Ca(1)-O(2) bond length. There is one shorter (2.38 Å) and one longer (2.42 Å) Ca(1)-O(4) bond length. In the second Ca site, Ca(2) is bonded to one O(1), one O(2), one O(3), one O(4), one O(5), and one O(6) atom to form distorted edge-sharing CaO6 octahedra. The Ca(2)-O(1) bond length is 2.34 Å. The Ca(2)-O(2) bond length is 2.55 Å. The Ca(2)-O(3) bond length is 2.33 Å. The Ca(2)-O(4) bond length is 2.48 Å. The Ca(2)-O(5) bond length is 2.35 Å. The Ca(2)-O(6) bond length is 2.33 Å. In the third Ca site, Ca(3) is bonded in a 8-coordinate geometry to two equivalent O(1), two equivalent O(3), two equivalent O(5), and two equivalent O(6) atoms. Both Ca(3)-O(1) bond lengths are 2.81 Å. Both Ca(3)-O(3) bond lengths are 2.32 Å. Both Ca(3)-O(5) bond lengths are 2.80 Å. Both Ca(3)-O(6) bond lengths are 2.31 Å. 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(1) and two equivalent O(2) atoms. Both Cu(1)-O(1) bond lengths are 1.97 Å. Both Cu(1)-O(2) bond lengths are 2.01 Å. In the second Cu site, Cu(2) is bonded in a rectangular see-saw-like geometry to one O(1), one O(2), and two equivalent O(3) atoms. The Cu(2)-O(1) bond length is 1.90 Å. The Cu(2)-O(2) bond length is 1.91 Å. Both Cu(2)-O(3) bond lengths are 1.91 Å. In the third Cu site, Cu(3) is bonded in a rectangular see-saw-like geometry to one O(5), one O(6), and two equivalent O(4) atoms. The Cu(3)-O(5) bond length is 1.99 Å. The Cu(3)-O(6) bond length is 1.93 Å. There is one shorter (1.95 Å) and one longer (1.97 Å) Cu(3)-O(4) bond length. In the fourth Cu site, Cu(4) is bonded in a square co-planar geometry to two equivalent O(5) and two equivalent O(6) atoms. Both Cu(4)-O(5) bond lengths are 1.89 Å. Both Cu(4)-O(6) bond lengths are 1.87 Å. There are six inequivalent O sites. In the first O site, O(4) is bonded to one Ca(2), two equivalent Ca(1), and two equivalent Cu(3) atoms to form distorted OCa3Cu2 square pyramids that share corners with three equivalent O(2)Ca3Cu2 trigonal bipyramids,  a cornercorner with one O(3)Ca2Cu2 trigonal pyramid, edges with two equivalent O(4)Ca3Cu2 square pyramids, and  an edgeedge with one O(2)Ca3Cu2 trigonal bipyramid. In the second O site, O(5) is bonded in a 5-coordinate geometry to one Ca(1), one Ca(2), one Ca(3), one Cu(3), and one Cu(4) atom. In the third O site, O(6) is bonded in a distorted see-saw-like geometry to one Ca(2), one Ca(3), one Cu(3), and one Cu(4) atom. In the fourth O site, O(1) is bonded in a 5-coordinate geometry to one Ca(1), one Ca(2), one Ca(3), one Cu(1), and one Cu(2) atom. In the fifth O site, O(2) is bonded to one Ca(2), two equivalent Ca(1), one Cu(1), and one Cu(2) atom to form distorted OCa3Cu2 trigonal bipyramids that share corners with three equivalent O(4)Ca3Cu2 square pyramids,  a cornercorner with one O(2)Ca3Cu2 trigonal bipyramid,  a cornercorner with one O(3)Ca2Cu2 trigonal pyramid,  an edgeedge with one O(4)Ca3Cu2 square pyramid,  an edgeedge with one O(2)Ca3Cu2 trigonal bipyramid, and  an edgeedge with one O(3)Ca2Cu2 trigonal pyramid. In the sixth O site, O(3) is bonded to one Ca(2), one Ca(3), and two equivalent Cu(2) atoms to form distorted OCa2Cu2 trigonal pyramids that share  a cornercorner with one O(4)Ca3Cu2 square pyramid,  a cornercorner with one O(2)Ca3Cu2 trigonal bipyramid,  a cornercorner with one O(3)Ca2Cu2 trigonal pyramid,  an edgeedge with one O(2)Ca3Cu2 trigonal bipyramid, and  an edgeedge with one O(3)Ca2Cu2 trigonal pyramid.