CsLu2Cu3Se5 crystallizes in the orthorhombic Cmcm space group. Cs(1) is bonded in a 10-coordinate geometry to two equivalent Cu(1), two equivalent Se(1), two equivalent Se(2), and four equivalent Se(3) atoms. Lu(1) is bonded to one Se(1), two equivalent Se(3), and three equivalent Se(2) atoms to form LuSe6 octahedra that share  a cornercorner with one Lu(1)Se6 octahedra, corners with four equivalent Cu(2)Se4 tetrahedra, edges with four equivalent Lu(1)Se6 octahedra, edges with two equivalent Cu(1)Cs2Se4 tetrahedra, and edges with three equivalent Cu(2)Se4 tetrahedra. The corner-sharing octahedral tilt angles are 27°. There are two inequivalent Cu sites. In the first Cu site, Cu(1) is bonded to two equivalent Cs(1), two equivalent Se(1), and two equivalent Se(3) atoms to form distorted CuCs2Se4 tetrahedra that share corners with four equivalent Se(2)CsLu3Cu2 octahedra, corners with four equivalent Cu(2)Se4 tetrahedra, edges with four equivalent Lu(1)Se6 octahedra, and edges with two equivalent Cu(1)Cs2Se4 tetrahedra. The corner-sharing octahedral tilt angles are 67°. In the second Cu site, Cu(2) is bonded to two equivalent Se(2) and two equivalent Se(3) atoms to form distorted CuSe4 tetrahedra that share corners with four equivalent Lu(1)Se6 octahedra, corners with two equivalent Cu(1)Cs2Se4 tetrahedra, corners with two equivalent Cu(2)Se4 tetrahedra, edges with three equivalent Lu(1)Se6 octahedra, and  an edgeedge with one Cu(2)Se4 tetrahedra. The corner-sharing octahedral tilt angles range from 13-60°. There are three inequivalent Se sites. In the first Se site, Se(1) is bonded in a 6-coordinate geometry to two equivalent Cs(1), two equivalent Lu(1), and two equivalent Cu(1) atoms. In the second Se site, Se(2) is bonded to one Cs(1), three equivalent Lu(1), and two equivalent Cu(2) atoms to form distorted SeCsLu3Cu2 octahedra that share  a cornercorner with one Se(2)CsLu3Cu2 octahedra, corners with two equivalent Cu(1)Cs2Se4 tetrahedra, and edges with four equivalent Se(2)CsLu3Cu2 octahedra. The corner-sharing octahedral tilt angles are 54°. In the third Se site, Se(3) is bonded in a 7-coordinate geometry to two equivalent Cs(1), two equivalent Lu(1), one Cu(1), and two equivalent Cu(2) atoms.
CsLu2Cu3Se5 crystallizes in the orthorhombic Cmcm space group. Cs(1) is bonded in a 10-coordinate geometry to two equivalent Cu(1), two equivalent Se(1), two equivalent Se(2), and four equivalent Se(3) atoms. Both Cs(1)-Cu(1) bond lengths are 3.75 Å. Both Cs(1)-Se(1) bond lengths are 3.56 Å. Both Cs(1)-Se(2) bond lengths are 3.48 Å. All Cs(1)-Se(3) bond lengths are 3.60 Å. Lu(1) is bonded to one Se(1), two equivalent Se(3), and three equivalent Se(2) atoms to form LuSe6 octahedra that share  a cornercorner with one Lu(1)Se6 octahedra, corners with four equivalent Cu(2)Se4 tetrahedra, edges with four equivalent Lu(1)Se6 octahedra, edges with two equivalent Cu(1)Cs2Se4 tetrahedra, and edges with three equivalent Cu(2)Se4 tetrahedra. The corner-sharing octahedral tilt angles are 27°. The Lu(1)-Se(1) bond length is 2.77 Å. Both Lu(1)-Se(3) bond lengths are 2.79 Å. There is one shorter (2.77 Å) and two longer (2.87 Å) Lu(1)-Se(2) bond lengths. There are two inequivalent Cu sites. In the first Cu site, Cu(1) is bonded to two equivalent Cs(1), two equivalent Se(1), and two equivalent Se(3) atoms to form distorted CuCs2Se4 tetrahedra that share corners with four equivalent Se(2)CsLu3Cu2 octahedra, corners with four equivalent Cu(2)Se4 tetrahedra, edges with four equivalent Lu(1)Se6 octahedra, and edges with two equivalent Cu(1)Cs2Se4 tetrahedra. The corner-sharing octahedral tilt angles are 67°. Both Cu(1)-Se(1) bond lengths are 2.36 Å. Both Cu(1)-Se(3) bond lengths are 2.70 Å. In the second Cu site, Cu(2) is bonded to two equivalent Se(2) and two equivalent Se(3) atoms to form distorted CuSe4 tetrahedra that share corners with four equivalent Lu(1)Se6 octahedra, corners with two equivalent Cu(1)Cs2Se4 tetrahedra, corners with two equivalent Cu(2)Se4 tetrahedra, edges with three equivalent Lu(1)Se6 octahedra, and  an edgeedge with one Cu(2)Se4 tetrahedra. The corner-sharing octahedral tilt angles range from 13-60°. Both Cu(2)-Se(2) bond lengths are 2.49 Å. There is one shorter (2.49 Å) and one longer (2.51 Å) Cu(2)-Se(3) bond length. There are three inequivalent Se sites. In the first Se site, Se(1) is bonded in a 6-coordinate geometry to two equivalent Cs(1), two equivalent Lu(1), and two equivalent Cu(1) atoms. In the second Se site, Se(2) is bonded to one Cs(1), three equivalent Lu(1), and two equivalent Cu(2) atoms to form distorted SeCsLu3Cu2 octahedra that share  a cornercorner with one Se(2)CsLu3Cu2 octahedra, corners with two equivalent Cu(1)Cs2Se4 tetrahedra, and edges with four equivalent Se(2)CsLu3Cu2 octahedra. The corner-sharing octahedral tilt angles are 54°. In the third Se site, Se(3) is bonded in a 7-coordinate geometry to two equivalent Cs(1), two equivalent Lu(1), one Cu(1), and two equivalent Cu(2) atoms.