Cr4Cu3Se8 crystallizes in the orthorhombic Imm2 space group. There are two inequivalent Cr sites. In the first Cr site, Cr(1) is bonded to one Se(1), one Se(4), two equivalent Se(2), and two equivalent Se(3) atoms to form CrSe6 octahedra that share corners with three equivalent Cu(1)CuSe4 tetrahedra, corners with three equivalent Cu(3)Se4 tetrahedra, and edges with two equivalent Cr(1)Se6 octahedra. In the second Cr site, Cr(2) is bonded in a 7-coordinate geometry to one Cu(2), one Se(2), one Se(3), two equivalent Se(1), and two equivalent Se(4) atoms. There are three inequivalent Cu sites. In the first Cu site, Cu(1) is bonded to one Cu(2), two equivalent Se(1), and two equivalent Se(2) atoms to form distorted CuCuSe4 tetrahedra that share corners with six equivalent Cr(1)Se6 octahedra and corners with two equivalent Se(4)Cr3Cu2 square pyramids. The corner-sharing octahedral tilt angles range from 57-60°. In the second Cu site, Cu(2) is bonded in a 7-coordinate geometry to two equivalent Cr(2), one Cu(1), two equivalent Se(2), and two equivalent Se(4) atoms. In the third Cu site, Cu(3) is bonded to two equivalent Se(3) and two equivalent Se(4) atoms to form CuSe4 tetrahedra that share corners with six equivalent Cr(1)Se6 octahedra. The corner-sharing octahedral tilt angles range from 53-56°. There are four inequivalent Se sites. In the first Se site, Se(1) is bonded to one Cr(1), two equivalent Cr(2), and one Cu(1) atom to form distorted SeCr3Cu trigonal pyramids that share corners with five equivalent Se(4)Cr3Cu2 square pyramids,  a cornercorner with one Se(1)Cr3Cu trigonal pyramid, corners with four equivalent Se(3)Cr3Cu trigonal pyramids, and  an edgeedge with one Se(1)Cr3Cu trigonal pyramid. In the second Se site, Se(2) is bonded in a 5-coordinate geometry to one Cr(2), two equivalent Cr(1), one Cu(1), and one Cu(2) atom. In the third Se site, Se(3) is bonded to one Cr(2), two equivalent Cr(1), and one Cu(3) atom to form distorted SeCr3Cu trigonal pyramids that share corners with two equivalent Se(4)Cr3Cu2 square pyramids,  a cornercorner with one Se(3)Cr3Cu trigonal pyramid, corners with four equivalent Se(1)Cr3Cu trigonal pyramids, edges with two equivalent Se(4)Cr3Cu2 square pyramids, and  an edgeedge with one Se(3)Cr3Cu trigonal pyramid. In the fourth Se site, Se(4) is bonded to one Cr(1), two equivalent Cr(2), one Cu(2), and one Cu(3) atom to form distorted SeCr3Cu2 square pyramids that share  a cornercorner with one Se(4)Cr3Cu2 square pyramid,  a cornercorner with one Cu(1)CuSe4 tetrahedra, corners with two equivalent Se(3)Cr3Cu trigonal pyramids, corners with five equivalent Se(1)Cr3Cu trigonal pyramids, edges with two equivalent Se(3)Cr3Cu trigonal pyramids, and  a faceface with one Se(4)Cr3Cu2 square pyramid.
Cr4Cu3Se8 crystallizes in the orthorhombic Imm2 space group. There are two inequivalent Cr sites. In the first Cr site, Cr(1) is bonded to one Se(1), one Se(4), two equivalent Se(2), and two equivalent Se(3) atoms to form CrSe6 octahedra that share corners with three equivalent Cu(1)CuSe4 tetrahedra, corners with three equivalent Cu(3)Se4 tetrahedra, and edges with two equivalent Cr(1)Se6 octahedra. The Cr(1)-Se(1) bond length is 2.53 Å. The Cr(1)-Se(4) bond length is 2.57 Å. Both Cr(1)-Se(2) bond lengths are 2.54 Å. Both Cr(1)-Se(3) bond lengths are 2.52 Å. In the second Cr site, Cr(2) is bonded in a 7-coordinate geometry to one Cu(2), one Se(2), one Se(3), two equivalent Se(1), and two equivalent Se(4) atoms. The Cr(2)-Cu(2) bond length is 2.57 Å. The Cr(2)-Se(2) bond length is 2.75 Å. The Cr(2)-Se(3) bond length is 2.51 Å. Both Cr(2)-Se(1) bond lengths are 2.52 Å. Both Cr(2)-Se(4) bond lengths are 2.64 Å. There are three inequivalent Cu sites. In the first Cu site, Cu(1) is bonded to one Cu(2), two equivalent Se(1), and two equivalent Se(2) atoms to form distorted CuCuSe4 tetrahedra that share corners with six equivalent Cr(1)Se6 octahedra and corners with two equivalent Se(4)Cr3Cu2 square pyramids. The corner-sharing octahedral tilt angles range from 57-60°. The Cu(1)-Cu(2) bond length is 2.48 Å. Both Cu(1)-Se(1) bond lengths are 2.39 Å. Both Cu(1)-Se(2) bond lengths are 2.52 Å. In the second Cu site, Cu(2) is bonded in a 7-coordinate geometry to two equivalent Cr(2), one Cu(1), two equivalent Se(2), and two equivalent Se(4) atoms. Both Cu(2)-Se(2) bond lengths are 2.35 Å. Both Cu(2)-Se(4) bond lengths are 2.46 Å. In the third Cu site, Cu(3) is bonded to two equivalent Se(3) and two equivalent Se(4) atoms to form CuSe4 tetrahedra that share corners with six equivalent Cr(1)Se6 octahedra. The corner-sharing octahedral tilt angles range from 53-56°. Both Cu(3)-Se(3) bond lengths are 2.41 Å. Both Cu(3)-Se(4) bond lengths are 2.44 Å. There are four inequivalent Se sites. In the first Se site, Se(1) is bonded to one Cr(1), two equivalent Cr(2), and one Cu(1) atom to form distorted SeCr3Cu trigonal pyramids that share corners with five equivalent Se(4)Cr3Cu2 square pyramids,  a cornercorner with one Se(1)Cr3Cu trigonal pyramid, corners with four equivalent Se(3)Cr3Cu trigonal pyramids, and  an edgeedge with one Se(1)Cr3Cu trigonal pyramid. In the second Se site, Se(2) is bonded in a 5-coordinate geometry to one Cr(2), two equivalent Cr(1), one Cu(1), and one Cu(2) atom. In the third Se site, Se(3) is bonded to one Cr(2), two equivalent Cr(1), and one Cu(3) atom to form distorted SeCr3Cu trigonal pyramids that share corners with two equivalent Se(4)Cr3Cu2 square pyramids,  a cornercorner with one Se(3)Cr3Cu trigonal pyramid, corners with four equivalent Se(1)Cr3Cu trigonal pyramids, edges with two equivalent Se(4)Cr3Cu2 square pyramids, and  an edgeedge with one Se(3)Cr3Cu trigonal pyramid. In the fourth Se site, Se(4) is bonded to one Cr(1), two equivalent Cr(2), one Cu(2), and one Cu(3) atom to form distorted SeCr3Cu2 square pyramids that share  a cornercorner with one Se(4)Cr3Cu2 square pyramid,  a cornercorner with one Cu(1)CuSe4 tetrahedra, corners with two equivalent Se(3)Cr3Cu trigonal pyramids, corners with five equivalent Se(1)Cr3Cu trigonal pyramids, edges with two equivalent Se(3)Cr3Cu trigonal pyramids, and  a faceface with one Se(4)Cr3Cu2 square pyramid.