HoCuSe2 crystallizes in the trigonal P3m1 space group. Ho(1) is bonded to three equivalent Se(1) and three equivalent Se(2) atoms to form HoSe6 octahedra that share corners with six equivalent Cu(1)Se4 tetrahedra, edges with six equivalent Ho(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 Ho(1)Se6 octahedra, corners with six equivalent Cu(1)Se4 tetrahedra, and edges with three equivalent Ho(1)Se6 octahedra. The corner-sharing octahedral tilt angles range from 19-57°. There are two inequivalent Se sites. In the first Se site, Se(1) is bonded in a distorted rectangular see-saw-like geometry to three equivalent Ho(1) and one Cu(1) atom. In the second Se site, Se(2) is bonded to three equivalent Ho(1) and three equivalent Cu(1) atoms to form distorted edge-sharing SeHo3Cu3 octahedra.
HoCuSe2 crystallizes in the trigonal P3m1 space group. Ho(1) is bonded to three equivalent Se(1) and three equivalent Se(2) atoms to form HoSe6 octahedra that share corners with six equivalent Cu(1)Se4 tetrahedra, edges with six equivalent Ho(1)Se6 octahedra, and edges with three equivalent Cu(1)Se4 tetrahedra. All Ho(1)-Se(1) bond lengths are 2.79 Å. All Ho(1)-Se(2) bond lengths are 2.92 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 Ho(1)Se6 octahedra, corners with six equivalent Cu(1)Se4 tetrahedra, and edges with three equivalent Ho(1)Se6 octahedra. The corner-sharing octahedral tilt angles range from 19-57°. The Cu(1)-Se(1) bond length is 2.43 Å. All Cu(1)-Se(2) bond lengths are 2.45 Å. There are two inequivalent Se sites. In the first Se site, Se(1) is bonded in a distorted rectangular see-saw-like geometry to three equivalent Ho(1) and one Cu(1) atom. In the second Se site, Se(2) is bonded to three equivalent Ho(1) and three equivalent Cu(1) atoms to form distorted edge-sharing SeHo3Cu3 octahedra.