YbCuSe2 crystallizes in the trigonal P3m1 space group. Yb(1) is bonded to three equivalent Se(1) and three equivalent Se(2) atoms to form YbSe6 octahedra that share corners with six equivalent Cu(1)Se4 tetrahedra, edges with six equivalent Yb(1)Se6 octahedra, and edges with three equivalent Cu(1)Se4 tetrahedra. Cu(1) is bonded to one Se(1) and three equivalent Se(2) atoms to form CuSe4 tetrahedra that share corners with six equivalent Yb(1)Se6 octahedra, corners with six equivalent Cu(1)Se4 tetrahedra, and edges with three equivalent Yb(1)Se6 octahedra. The corner-sharing octahedral tilt angles range from 20-55°. There are two inequivalent Se sites. In the first Se site, Se(1) is bonded in a rectangular see-saw-like geometry to three equivalent Yb(1) and one Cu(1) atom. In the second Se site, Se(2) is bonded to three equivalent Yb(1) and three equivalent Cu(1) atoms to form distorted edge-sharing SeYb3Cu3 octahedra.
YbCuSe2 crystallizes in the trigonal P3m1 space group. Yb(1) is bonded to three equivalent Se(1) and three equivalent Se(2) atoms to form YbSe6 octahedra that share corners with six equivalent Cu(1)Se4 tetrahedra, edges with six equivalent Yb(1)Se6 octahedra, and edges with three equivalent Cu(1)Se4 tetrahedra. All Yb(1)-Se(1) bond lengths are 2.86 Å. All Yb(1)-Se(2) bond lengths are 2.98 Å. Cu(1) is bonded to one Se(1) and three equivalent Se(2) atoms to form CuSe4 tetrahedra that share corners with six equivalent Yb(1)Se6 octahedra, corners with six equivalent Cu(1)Se4 tetrahedra, and edges with three equivalent Yb(1)Se6 octahedra. The corner-sharing octahedral tilt angles range from 20-55°. The Cu(1)-Se(1) bond length is 2.36 Å. All Cu(1)-Se(2) bond lengths are 2.47 Å. There are two inequivalent Se sites. In the first Se site, Se(1) is bonded in a rectangular see-saw-like geometry to three equivalent Yb(1) and one Cu(1) atom. In the second Se site, Se(2) is bonded to three equivalent Yb(1) and three equivalent Cu(1) atoms to form distorted edge-sharing SeYb3Cu3 octahedra.