DyCuSe2 crystallizes in the trigonal P3m1 space group. Dy(1) is bonded to three equivalent Se(1) and three equivalent Se(2) atoms to form DySe6 octahedra that share corners with six equivalent Cu(1)Se4 tetrahedra, edges with six equivalent Dy(1)Se6 octahedra, and edges with three equivalent Cu(1)Se4 tetrahedra. Cu(1) is bonded to one Se(2) and three equivalent Se(1) atoms to form CuSe4 tetrahedra that share corners with six equivalent Dy(1)Se6 octahedra, corners with six equivalent Cu(1)Se4 tetrahedra, and edges with three equivalent Dy(1)Se6 octahedra. The corner-sharing octahedral tilt angles range from 20-57°. There are two inequivalent Se sites. In the first Se site, Se(1) is bonded to three equivalent Dy(1) and three equivalent Cu(1) atoms to form distorted edge-sharing SeDy3Cu3 octahedra. In the second Se site, Se(2) is bonded in a distorted rectangular see-saw-like geometry to three equivalent Dy(1) and one Cu(1) atom.
DyCuSe2 crystallizes in the trigonal P3m1 space group. Dy(1) is bonded to three equivalent Se(1) and three equivalent Se(2) atoms to form DySe6 octahedra that share corners with six equivalent Cu(1)Se4 tetrahedra, edges with six equivalent Dy(1)Se6 octahedra, and edges with three equivalent Cu(1)Se4 tetrahedra. All Dy(1)-Se(1) bond lengths are 2.93 Å. All Dy(1)-Se(2) bond lengths are 2.79 Å. Cu(1) is bonded to one Se(2) and three equivalent Se(1) atoms to form CuSe4 tetrahedra that share corners with six equivalent Dy(1)Se6 octahedra, corners with six equivalent Cu(1)Se4 tetrahedra, and edges with three equivalent Dy(1)Se6 octahedra. The corner-sharing octahedral tilt angles range from 20-57°. The Cu(1)-Se(2) bond length is 2.43 Å. All Cu(1)-Se(1) bond lengths are 2.46 Å. There are two inequivalent Se sites. In the first Se site, Se(1) is bonded to three equivalent Dy(1) and three equivalent Cu(1) atoms to form distorted edge-sharing SeDy3Cu3 octahedra. In the second Se site, Se(2) is bonded in a distorted rectangular see-saw-like geometry to three equivalent Dy(1) and one Cu(1) atom.