Cr10Co4CuSe20 crystallizes in the monoclinic C2/m space group. There are five inequivalent Cr sites. In the first Cr site, Cr(1) is bonded to one Se(1), one Se(6), two equivalent Se(3), and two equivalent Se(8) atoms to form distorted CrSe6 octahedra that share corners with two equivalent Co(2)Se6 octahedra, corners with four equivalent Co(1)Se6 octahedra, edges with two equivalent Cr(1)Se6 octahedra, edges with four equivalent Cr(3)Se6 octahedra, and  a faceface with one Co(2)Se6 octahedra. The corner-sharing octahedral tilt angles range from 49-53°. In the second Cr site, Cr(2) is bonded to three equivalent Se(2) and three equivalent Se(7) atoms to form distorted CrSe6 octahedra that share corners with six equivalent Co(2)Se6 octahedra, edges with six equivalent Cr(2)Se6 octahedra, and  a faceface with one Co(2)Se6 octahedra. The corner-sharing octahedral tilt angles range from 49-53°. In the third Cr site, Cr(3) is bonded to one Se(3), one Se(8), two equivalent Se(1), and two equivalent Se(6) atoms to form distorted CrSe6 octahedra that share corners with two equivalent Co(1)Se6 octahedra, corners with four equivalent Co(2)Se6 octahedra, edges with two equivalent Cr(3)Se6 octahedra, edges with four equivalent Cr(1)Se6 octahedra, and  a faceface with one Co(1)Se6 octahedra. The corner-sharing octahedral tilt angles range from 49-53°. In the fourth Cr site, Cr(4) is bonded to one Se(4), one Se(9), two equivalent Se(10), and two equivalent Se(5) atoms to form distorted CrSe6 octahedra that share corners with two equivalent Cu(1)Se6 octahedra, corners with four equivalent Co(1)Se6 octahedra, edges with two equivalent Cr(4)Se6 octahedra, edges with four equivalent Cr(5)Se6 octahedra, and  a faceface with one Cu(1)Se6 octahedra. The corner-sharing octahedral tilt angles range from 50-53°. In the fifth Cr site, Cr(5) is bonded to one Se(10), one Se(5), two equivalent Se(4), and two equivalent Se(9) atoms to form distorted CrSe6 octahedra that share corners with two equivalent Co(1)Se6 octahedra, corners with four equivalent Cu(1)Se6 octahedra, edges with two equivalent Cr(5)Se6 octahedra, edges with four equivalent Cr(4)Se6 octahedra, and  a faceface with one Co(1)Se6 octahedra. The corner-sharing octahedral tilt angles range from 48-52°. There are two inequivalent Co sites. In the first Co site, Co(1) is bonded to one Se(3), one Se(5), two equivalent Se(6), and two equivalent Se(9) atoms to form CoSe6 octahedra that share corners with two equivalent Cr(3)Se6 octahedra, corners with two equivalent Cr(5)Se6 octahedra, corners with four equivalent Cr(1)Se6 octahedra, corners with four equivalent Cr(4)Se6 octahedra, edges with two equivalent Co(1)Se6 octahedra,  a faceface with one Cr(3)Se6 octahedra, and  a faceface with one Cr(5)Se6 octahedra. The corner-sharing octahedral tilt angles range from 48-53°. In the second Co site, Co(2) is bonded to one Se(1), one Se(2), two equivalent Se(7), and two equivalent Se(8) atoms to form CoSe6 octahedra that share corners with two equivalent Cr(1)Se6 octahedra, corners with four equivalent Cr(3)Se6 octahedra, corners with six equivalent Cr(2)Se6 octahedra, edges with two equivalent Co(2)Se6 octahedra,  a faceface with one Cr(1)Se6 octahedra, and  a faceface with one Cr(2)Se6 octahedra. The corner-sharing octahedral tilt angles range from 49-53°. Cu(1) is bonded to two equivalent Se(4) and four equivalent Se(10) atoms to form CuSe6 octahedra that share corners with four equivalent Cr(4)Se6 octahedra, corners with eight equivalent Cr(5)Se6 octahedra, edges with two equivalent Cu(1)Se6 octahedra, and faces with two equivalent Cr(4)Se6 octahedra. The corner-sharing octahedral tilt angles range from 50-52°. There are ten inequivalent Se sites. In the first Se site, Se(3) is bonded in a rectangular see-saw-like geometry to one Cr(3), two equivalent Cr(1), and one Co(1) atom. In the second Se site, Se(4) is bonded in a rectangular see-saw-like geometry to one Cr(4), two equivalent Cr(5), and one Cu(1) atom. In the third Se site, Se(5) is bonded in a rectangular see-saw-like geometry to one Cr(5), two equivalent Cr(4), and one Co(1) atom. In the fourth Se site, Se(6) is bonded to one Cr(1), two equivalent Cr(3), and two equivalent Co(1) atoms to form a mixture of distorted edge and corner-sharing SeCr3Co2 square pyramids. In the fifth Se site, Se(7) is bonded to three equivalent Cr(2) and two equivalent Co(2) atoms to form a mixture of distorted edge and corner-sharing SeCr3Co2 square pyramids. In the sixth Se site, Se(8) is bonded to one Cr(3), two equivalent Cr(1), and two equivalent Co(2) atoms to form a mixture of distorted edge and corner-sharing SeCr3Co2 square pyramids. In the seventh Se site, Se(9) is bonded to one Cr(4), two equivalent Cr(5), and two equivalent Co(1) atoms to form a mixture of distorted edge and corner-sharing SeCr3Co2 square pyramids. In the eighth Se site, Se(10) is bonded in a 5-coordinate geometry to one Cr(5), two equivalent Cr(4), and two equivalent Cu(1) atoms. In the ninth Se site, Se(1) is bonded in a rectangular see-saw-like geometry to one Cr(1), two equivalent Cr(3), and one Co(2) atom. In the tenth Se site, Se(2) is bonded in a rectangular see-saw-like geometry to three equivalent Cr(2) and one Co(2) atom.
Cr10Co4CuSe20 crystallizes in the monoclinic C2/m space group. There are five inequivalent Cr sites. In the first Cr site, Cr(1) is bonded to one Se(1), one Se(6), two equivalent Se(3), and two equivalent Se(8) atoms to form distorted CrSe6 octahedra that share corners with two equivalent Co(2)Se6 octahedra, corners with four equivalent Co(1)Se6 octahedra, edges with two equivalent Cr(1)Se6 octahedra, edges with four equivalent Cr(3)Se6 octahedra, and  a faceface with one Co(2)Se6 octahedra. The corner-sharing octahedral tilt angles range from 49-53°. The Cr(1)-Se(1) bond length is 2.50 Å. The Cr(1)-Se(6) bond length is 2.62 Å. Both Cr(1)-Se(3) bond lengths are 2.50 Å. Both Cr(1)-Se(8) bond lengths are 2.62 Å. In the second Cr site, Cr(2) is bonded to three equivalent Se(2) and three equivalent Se(7) atoms to form distorted CrSe6 octahedra that share corners with six equivalent Co(2)Se6 octahedra, edges with six equivalent Cr(2)Se6 octahedra, and  a faceface with one Co(2)Se6 octahedra. The corner-sharing octahedral tilt angles range from 49-53°. There is one shorter (2.50 Å) and two longer (2.51 Å) Cr(2)-Se(2) bond lengths. All Cr(2)-Se(7) bond lengths are 2.62 Å. In the third Cr site, Cr(3) is bonded to one Se(3), one Se(8), two equivalent Se(1), and two equivalent Se(6) atoms to form distorted CrSe6 octahedra that share corners with two equivalent Co(1)Se6 octahedra, corners with four equivalent Co(2)Se6 octahedra, edges with two equivalent Cr(3)Se6 octahedra, edges with four equivalent Cr(1)Se6 octahedra, and  a faceface with one Co(1)Se6 octahedra. The corner-sharing octahedral tilt angles range from 49-53°. The Cr(3)-Se(3) bond length is 2.50 Å. The Cr(3)-Se(8) bond length is 2.62 Å. Both Cr(3)-Se(1) bond lengths are 2.50 Å. Both Cr(3)-Se(6) bond lengths are 2.62 Å. In the fourth Cr site, Cr(4) is bonded to one Se(4), one Se(9), two equivalent Se(10), and two equivalent Se(5) atoms to form distorted CrSe6 octahedra that share corners with two equivalent Cu(1)Se6 octahedra, corners with four equivalent Co(1)Se6 octahedra, edges with two equivalent Cr(4)Se6 octahedra, edges with four equivalent Cr(5)Se6 octahedra, and  a faceface with one Cu(1)Se6 octahedra. The corner-sharing octahedral tilt angles range from 50-53°. The Cr(4)-Se(4) bond length is 2.53 Å. The Cr(4)-Se(9) bond length is 2.64 Å. Both Cr(4)-Se(10) bond lengths are 2.56 Å. Both Cr(4)-Se(5) bond lengths are 2.51 Å. In the fifth Cr site, Cr(5) is bonded to one Se(10), one Se(5), two equivalent Se(4), and two equivalent Se(9) atoms to form distorted CrSe6 octahedra that share corners with two equivalent Co(1)Se6 octahedra, corners with four equivalent Cu(1)Se6 octahedra, edges with two equivalent Cr(5)Se6 octahedra, edges with four equivalent Cr(4)Se6 octahedra, and  a faceface with one Co(1)Se6 octahedra. The corner-sharing octahedral tilt angles range from 48-52°. The Cr(5)-Se(10) bond length is 2.53 Å. The Cr(5)-Se(5) bond length is 2.50 Å. Both Cr(5)-Se(4) bond lengths are 2.48 Å. Both Cr(5)-Se(9) bond lengths are 2.63 Å. There are two inequivalent Co sites. In the first Co site, Co(1) is bonded to one Se(3), one Se(5), two equivalent Se(6), and two equivalent Se(9) atoms to form CoSe6 octahedra that share corners with two equivalent Cr(3)Se6 octahedra, corners with two equivalent Cr(5)Se6 octahedra, corners with four equivalent Cr(1)Se6 octahedra, corners with four equivalent Cr(4)Se6 octahedra, edges with two equivalent Co(1)Se6 octahedra,  a faceface with one Cr(3)Se6 octahedra, and  a faceface with one Cr(5)Se6 octahedra. The corner-sharing octahedral tilt angles range from 48-53°. The Co(1)-Se(3) bond length is 2.47 Å. The Co(1)-Se(5) bond length is 2.47 Å. Both Co(1)-Se(6) bond lengths are 2.51 Å. Both Co(1)-Se(9) bond lengths are 2.47 Å. In the second Co site, Co(2) is bonded to one Se(1), one Se(2), two equivalent Se(7), and two equivalent Se(8) atoms to form CoSe6 octahedra that share corners with two equivalent Cr(1)Se6 octahedra, corners with four equivalent Cr(3)Se6 octahedra, corners with six equivalent Cr(2)Se6 octahedra, edges with two equivalent Co(2)Se6 octahedra,  a faceface with one Cr(1)Se6 octahedra, and  a faceface with one Cr(2)Se6 octahedra. The corner-sharing octahedral tilt angles range from 49-53°. The Co(2)-Se(1) bond length is 2.48 Å. The Co(2)-Se(2) bond length is 2.48 Å. Both Co(2)-Se(7) bond lengths are 2.51 Å. Both Co(2)-Se(8) bond lengths are 2.51 Å. Cu(1) is bonded to two equivalent Se(4) and four equivalent Se(10) atoms to form CuSe6 octahedra that share corners with four equivalent Cr(4)Se6 octahedra, corners with eight equivalent Cr(5)Se6 octahedra, edges with two equivalent Cu(1)Se6 octahedra, and faces with two equivalent Cr(4)Se6 octahedra. The corner-sharing octahedral tilt angles range from 50-52°. Both Cu(1)-Se(4) bond lengths are 2.54 Å. All Cu(1)-Se(10) bond lengths are 2.61 Å. There are ten inequivalent Se sites. In the first Se site, Se(3) is bonded in a rectangular see-saw-like geometry to one Cr(3), two equivalent Cr(1), and one Co(1) atom. In the second Se site, Se(4) is bonded in a rectangular see-saw-like geometry to one Cr(4), two equivalent Cr(5), and one Cu(1) atom. In the third Se site, Se(5) is bonded in a rectangular see-saw-like geometry to one Cr(5), two equivalent Cr(4), and one Co(1) atom. In the fourth Se site, Se(6) is bonded to one Cr(1), two equivalent Cr(3), and two equivalent Co(1) atoms to form a mixture of distorted edge and corner-sharing SeCr3Co2 square pyramids. In the fifth Se site, Se(7) is bonded to three equivalent Cr(2) and two equivalent Co(2) atoms to form a mixture of distorted edge and corner-sharing SeCr3Co2 square pyramids. In the sixth Se site, Se(8) is bonded to one Cr(3), two equivalent Cr(1), and two equivalent Co(2) atoms to form a mixture of distorted edge and corner-sharing SeCr3Co2 square pyramids. In the seventh Se site, Se(9) is bonded to one Cr(4), two equivalent Cr(5), and two equivalent Co(1) atoms to form a mixture of distorted edge and corner-sharing SeCr3Co2 square pyramids. In the eighth Se site, Se(10) is bonded in a 5-coordinate geometry to one Cr(5), two equivalent Cr(4), and two equivalent Cu(1) atoms. In the ninth Se site, Se(1) is bonded in a rectangular see-saw-like geometry to one Cr(1), two equivalent Cr(3), and one Co(2) atom. In the tenth Se site, Se(2) is bonded in a rectangular see-saw-like geometry to three equivalent Cr(2) and one Co(2) atom.