CsSm2Cu3Se5 crystallizes in the orthorhombic Cmcm space group. Cs(1) is bonded in a 8-coordinate geometry to two equivalent Se(1), two equivalent Se(3), and four equivalent Se(2) atoms. Sm(1) is bonded to one Se(1), two equivalent Se(2), and three equivalent Se(3) atoms to form SmSe6 octahedra that share  a cornercorner with one Sm(1)Se6 octahedra, corners with four equivalent Cu(2)Se4 tetrahedra, edges with four equivalent Sm(1)Se6 octahedra, and edges with three equivalent Cu(2)Se4 tetrahedra. The corner-sharing octahedral tilt angles are 25°. There are two inequivalent Cu sites. In the first Cu site, Cu(1) is bonded in a 4-coordinate geometry to two equivalent Se(1) and two equivalent Se(2) atoms. In the second Cu site, Cu(2) is bonded to two equivalent Se(2) and two equivalent Se(3) atoms to form CuSe4 tetrahedra that share corners with four equivalent Sm(1)Se6 octahedra, corners with two equivalent Cu(2)Se4 tetrahedra, edges with three equivalent Sm(1)Se6 octahedra, and  an edgeedge with one Cu(2)Se4 tetrahedra. The corner-sharing octahedral tilt angles range from 16-61°. 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 Sm(1), and two equivalent Cu(1) atoms. In the second Se site, Se(2) is bonded in a 7-coordinate geometry to two equivalent Cs(1), two equivalent Sm(1), one Cu(1), and two equivalent Cu(2) atoms. In the third Se site, Se(3) is bonded to one Cs(1), three equivalent Sm(1), and two equivalent Cu(2) atoms to form a mixture of distorted corner and edge-sharing SeCsSm3Cu2 octahedra. The corner-sharing octahedral tilt angles are 53°.
CsSm2Cu3Se5 crystallizes in the orthorhombic Cmcm space group. Cs(1) is bonded in a 8-coordinate geometry to two equivalent Se(1), two equivalent Se(3), and four equivalent Se(2) atoms. Both Cs(1)-Se(1) bond lengths are 3.67 Å. Both Cs(1)-Se(3) bond lengths are 3.55 Å. All Cs(1)-Se(2) bond lengths are 3.72 Å. Sm(1) is bonded to one Se(1), two equivalent Se(2), and three equivalent Se(3) atoms to form SmSe6 octahedra that share  a cornercorner with one Sm(1)Se6 octahedra, corners with four equivalent Cu(2)Se4 tetrahedra, edges with four equivalent Sm(1)Se6 octahedra, and edges with three equivalent Cu(2)Se4 tetrahedra. The corner-sharing octahedral tilt angles are 25°. The Sm(1)-Se(1) bond length is 2.89 Å. Both Sm(1)-Se(2) bond lengths are 2.91 Å. There is one shorter (2.87 Å) and two longer (2.97 Å) Sm(1)-Se(3) bond lengths. There are two inequivalent Cu sites. In the first Cu site, Cu(1) is bonded in a 4-coordinate geometry to two equivalent Se(1) and two equivalent Se(2) atoms. Both Cu(1)-Se(1) bond lengths are 2.40 Å. Both Cu(1)-Se(2) bond lengths are 2.88 Å. In the second Cu site, Cu(2) is bonded to two equivalent Se(2) and two equivalent Se(3) atoms to form CuSe4 tetrahedra that share corners with four equivalent Sm(1)Se6 octahedra, corners with two equivalent Cu(2)Se4 tetrahedra, edges with three equivalent Sm(1)Se6 octahedra, and  an edgeedge with one Cu(2)Se4 tetrahedra. The corner-sharing octahedral tilt angles range from 16-61°. Both Cu(2)-Se(2) bond lengths are 2.51 Å. Both Cu(2)-Se(3) bond lengths are 2.57 Å. 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 Sm(1), and two equivalent Cu(1) atoms. In the second Se site, Se(2) is bonded in a 7-coordinate geometry to two equivalent Cs(1), two equivalent Sm(1), one Cu(1), and two equivalent Cu(2) atoms. In the third Se site, Se(3) is bonded to one Cs(1), three equivalent Sm(1), and two equivalent Cu(2) atoms to form a mixture of distorted corner and edge-sharing SeCsSm3Cu2 octahedra. The corner-sharing octahedral tilt angles are 53°.