CsDyCdSe3 crystallizes in the orthorhombic Cmcm space group. Cs(1) is bonded in a 8-coordinate geometry to two equivalent Se(1) and six equivalent Se(2) atoms. Dy(1) is bonded to two equivalent Se(1) and four equivalent Se(2) atoms to form DySe6 octahedra that share corners with two equivalent Dy(1)Se6 octahedra, edges with two equivalent Dy(1)Se6 octahedra, and edges with four equivalent Cd(1)Se4 tetrahedra. The corner-sharing octahedral tilt angles are 39°. Cd(1) is bonded to two equivalent Se(1) and two equivalent Se(2) atoms to form CdSe4 tetrahedra that share corners with two equivalent Cd(1)Se4 tetrahedra and edges with four equivalent Dy(1)Se6 octahedra. There are two inequivalent Se sites. In the first Se site, Se(1) is bonded in a 6-coordinate geometry to two equivalent Cs(1), two equivalent Dy(1), and two equivalent Cd(1) atoms. In the second Se site, Se(2) is bonded in a 6-coordinate geometry to three equivalent Cs(1), two equivalent Dy(1), and one Cd(1) atom.
CsDyCdSe3 crystallizes in the orthorhombic Cmcm space group. Cs(1) is bonded in a 8-coordinate geometry to two equivalent Se(1) and six equivalent Se(2) atoms. Both Cs(1)-Se(1) bond lengths are 3.70 Å. There are four shorter (3.89 Å) and two longer (3.91 Å) Cs(1)-Se(2) bond lengths. Dy(1) is bonded to two equivalent Se(1) and four equivalent Se(2) atoms to form DySe6 octahedra that share corners with two equivalent Dy(1)Se6 octahedra, edges with two equivalent Dy(1)Se6 octahedra, and edges with four equivalent Cd(1)Se4 tetrahedra. The corner-sharing octahedral tilt angles are 39°. Both Dy(1)-Se(1) bond lengths are 2.97 Å. All Dy(1)-Se(2) bond lengths are 2.92 Å. Cd(1) is bonded to two equivalent Se(1) and two equivalent Se(2) atoms to form CdSe4 tetrahedra that share corners with two equivalent Cd(1)Se4 tetrahedra and edges with four equivalent Dy(1)Se6 octahedra. Both Cd(1)-Se(1) bond lengths are 2.70 Å. Both Cd(1)-Se(2) bond lengths are 2.62 Å. There are two inequivalent Se sites. In the first Se site, Se(1) is bonded in a 6-coordinate geometry to two equivalent Cs(1), two equivalent Dy(1), and two equivalent Cd(1) atoms. In the second Se site, Se(2) is bonded in a 6-coordinate geometry to three equivalent Cs(1), two equivalent Dy(1), and one Cd(1) atom.