KCo3Cu(AsO4)3 crystallizes in the monoclinic C2/c space group. K(1) is bonded in a 8-coordinate geometry to two equivalent O(3), two equivalent O(4), and four equivalent O(6) atoms. There are two inequivalent Co sites. In the first Co site, Co(1) is bonded to one O(3), one O(4), one O(5), one O(6), and two equivalent O(2) atoms to form CoO6 octahedra that share corners with two equivalent As(2)O4 tetrahedra, corners with four equivalent As(1)O4 tetrahedra,  an edgeedge with one Co(1)O6 octahedra, and  an edgeedge with one Co(2)O6 pentagonal pyramid. In the second Co site, Co(2) is bonded to two equivalent O(1), two equivalent O(3), and two equivalent O(4) atoms to form distorted CoO6 pentagonal pyramids that share corners with two equivalent As(2)O4 tetrahedra, corners with four equivalent As(1)O4 tetrahedra, and edges with two equivalent Co(1)O6 octahedra. Cu(1) is bonded in a square co-planar geometry to two equivalent O(1) and two equivalent O(5) atoms. There are two inequivalent As sites. In the first As site, As(1) is bonded to one O(1), one O(2), one O(3), and one O(6) atom to form AsO4 tetrahedra that share corners with four equivalent Co(1)O6 octahedra and corners with two equivalent Co(2)O6 pentagonal pyramids. The corner-sharing octahedral tilt angles range from 38-61°. In the second As site, As(2) is bonded to two equivalent O(4) and two equivalent O(5) atoms to form AsO4 tetrahedra that share corners with four equivalent Co(1)O6 octahedra and corners with two equivalent Co(2)O6 pentagonal pyramids. The corner-sharing octahedral tilt angles range from 60-62°. There are six inequivalent O sites. In the first O site, O(1) is bonded in a distorted trigonal planar geometry to one Co(2), one Cu(1), and one As(1) atom. In the second O site, O(2) is bonded in a distorted trigonal planar geometry to two equivalent Co(1) and one As(1) atom. In the third O site, O(3) is bonded in a 3-coordinate geometry to one K(1), one Co(1), one Co(2), and one As(1) atom. In the fourth O site, O(4) is bonded in a 4-coordinate geometry to one K(1), one Co(1), one Co(2), and one As(2) atom. In the fifth O site, O(5) is bonded in a distorted trigonal planar geometry to one Co(1), one Cu(1), and one As(2) atom. In the sixth O site, O(6) is bonded to two equivalent K(1), one Co(1), and one As(1) atom to form a mixture of distorted corner and edge-sharing OK2CoAs trigonal pyramids.
KCo3Cu(AsO4)3 crystallizes in the monoclinic C2/c space group. K(1) is bonded in a 8-coordinate geometry to two equivalent O(3), two equivalent O(4), and four equivalent O(6) atoms. Both K(1)-O(3) bond lengths are 3.00 Å. Both K(1)-O(4) bond lengths are 2.94 Å. There are two shorter (2.67 Å) and two longer (2.70 Å) K(1)-O(6) bond lengths. There are two inequivalent Co sites. In the first Co site, Co(1) is bonded to one O(3), one O(4), one O(5), one O(6), and two equivalent O(2) atoms to form CoO6 octahedra that share corners with two equivalent As(2)O4 tetrahedra, corners with four equivalent As(1)O4 tetrahedra,  an edgeedge with one Co(1)O6 octahedra, and  an edgeedge with one Co(2)O6 pentagonal pyramid. The Co(1)-O(3) bond length is 2.14 Å. The Co(1)-O(4) bond length is 2.17 Å. The Co(1)-O(5) bond length is 2.09 Å. The Co(1)-O(6) bond length is 2.03 Å. There is one shorter (2.11 Å) and one longer (2.18 Å) Co(1)-O(2) bond length. In the second Co site, Co(2) is bonded to two equivalent O(1), two equivalent O(3), and two equivalent O(4) atoms to form distorted CoO6 pentagonal pyramids that share corners with two equivalent As(2)O4 tetrahedra, corners with four equivalent As(1)O4 tetrahedra, and edges with two equivalent Co(1)O6 octahedra. Both Co(2)-O(1) bond lengths are 2.10 Å. Both Co(2)-O(3) bond lengths are 2.16 Å. Both Co(2)-O(4) bond lengths are 2.21 Å. Cu(1) is bonded in a square co-planar geometry to two equivalent O(1) and two equivalent O(5) atoms. Both Cu(1)-O(1) bond lengths are 1.95 Å. Both Cu(1)-O(5) bond lengths are 1.97 Å. There are two inequivalent As sites. In the first As site, As(1) is bonded to one O(1), one O(2), one O(3), and one O(6) atom to form AsO4 tetrahedra that share corners with four equivalent Co(1)O6 octahedra and corners with two equivalent Co(2)O6 pentagonal pyramids. The corner-sharing octahedral tilt angles range from 38-61°. The As(1)-O(1) bond length is 1.75 Å. The As(1)-O(2) bond length is 1.73 Å. The As(1)-O(3) bond length is 1.74 Å. The As(1)-O(6) bond length is 1.71 Å. In the second As site, As(2) is bonded to two equivalent O(4) and two equivalent O(5) atoms to form AsO4 tetrahedra that share corners with four equivalent Co(1)O6 octahedra and corners with two equivalent Co(2)O6 pentagonal pyramids. The corner-sharing octahedral tilt angles range from 60-62°. Both As(2)-O(4) bond lengths are 1.73 Å. Both As(2)-O(5) bond lengths are 1.75 Å. There are six inequivalent O sites. In the first O site, O(1) is bonded in a distorted trigonal planar geometry to one Co(2), one Cu(1), and one As(1) atom. In the second O site, O(2) is bonded in a distorted trigonal planar geometry to two equivalent Co(1) and one As(1) atom. In the third O site, O(3) is bonded in a 3-coordinate geometry to one K(1), one Co(1), one Co(2), and one As(1) atom. In the fourth O site, O(4) is bonded in a 4-coordinate geometry to one K(1), one Co(1), one Co(2), and one As(2) atom. In the fifth O site, O(5) is bonded in a distorted trigonal planar geometry to one Co(1), one Cu(1), and one As(2) atom. In the sixth O site, O(6) is bonded to two equivalent K(1), one Co(1), and one As(1) atom to form a mixture of distorted corner and edge-sharing OK2CoAs trigonal pyramids.