Ho4CdSe7 crystallizes in the monoclinic Cm space group. There are four inequivalent Ho sites. In the first Ho site, Ho(1) is bonded in a 7-coordinate geometry to one Se(4), two equivalent Se(2), two equivalent Se(3), and two equivalent Se(5) atoms. In the second Ho site, Ho(2) is bonded in a 7-coordinate geometry to one Se(3), two equivalent Se(1), two equivalent Se(4), and two equivalent Se(6) atoms. In the third Ho site, Ho(3) is bonded to one Se(5), one Se(6), two equivalent Se(3), and two equivalent Se(4) atoms to form HoSe6 octahedra that share  a cornercorner with one Ho(4)Se6 octahedra,  a cornercorner with one Cd(1)Se6 octahedra, and edges with two equivalent Ho(3)Se6 octahedra. The corner-sharing octahedral tilt angles range from 54-56°. In the fourth Ho site, Ho(4) is bonded to one Se(2), one Se(6), two equivalent Se(1), and two equivalent Se(7) atoms to form HoSe6 octahedra that share  a cornercorner with one Ho(3)Se6 octahedra, corners with two equivalent Cd(1)Se6 octahedra, edges with two equivalent Ho(4)Se6 octahedra, and edges with three equivalent Cd(1)Se6 octahedra. The corner-sharing octahedral tilt angles range from 3-54°. Cd(1) is bonded to one Se(1), one Se(5), two equivalent Se(2), and two equivalent Se(7) atoms to form CdSe6 octahedra that share  a cornercorner with one Ho(3)Se6 octahedra, corners with two equivalent Ho(4)Se6 octahedra, edges with two equivalent Cd(1)Se6 octahedra, and edges with three equivalent Ho(4)Se6 octahedra. The corner-sharing octahedral tilt angles range from 3-56°. There are seven inequivalent Se sites. In the first Se site, Se(1) is bonded to two equivalent Ho(2), two equivalent Ho(4), and one Cd(1) atom to form SeHo4Cd trigonal bipyramids that share  a cornercorner with one Se(5)Ho3Cd tetrahedra, corners with four equivalent Se(6)Ho4 tetrahedra, corners with two equivalent Se(3)Ho5 trigonal bipyramids, corners with two equivalent Se(4)Ho5 trigonal bipyramids,  an edgeedge with one Se(6)Ho4 tetrahedra,  an edgeedge with one Se(4)Ho5 trigonal bipyramid, edges with two equivalent Se(2)Ho3Cd2 trigonal bipyramids, and edges with two equivalent Se(1)Ho4Cd trigonal bipyramids. In the second Se site, Se(2) is bonded to one Ho(4), two equivalent Ho(1), and two equivalent Cd(1) atoms to form SeHo3Cd2 trigonal bipyramids that share  a cornercorner with one Se(6)Ho4 tetrahedra, corners with four equivalent Se(5)Ho3Cd tetrahedra, corners with two equivalent Se(3)Ho5 trigonal bipyramids, corners with two equivalent Se(4)Ho5 trigonal bipyramids,  an edgeedge with one Se(5)Ho3Cd tetrahedra,  an edgeedge with one Se(3)Ho5 trigonal bipyramid, edges with two equivalent Se(2)Ho3Cd2 trigonal bipyramids, and edges with two equivalent Se(1)Ho4Cd trigonal bipyramids. In the third Se site, Se(3) is bonded to one Ho(2), two equivalent Ho(1), and two equivalent Ho(3) atoms to form distorted SeHo5 trigonal bipyramids that share corners with four equivalent Se(5)Ho3Cd tetrahedra, corners with two equivalent Se(2)Ho3Cd2 trigonal bipyramids, corners with two equivalent Se(1)Ho4Cd trigonal bipyramids, corners with two equivalent Se(4)Ho5 trigonal bipyramids,  an edgeedge with one Se(5)Ho3Cd tetrahedra, edges with two equivalent Se(6)Ho4 tetrahedra,  an edgeedge with one Se(2)Ho3Cd2 trigonal bipyramid, edges with two equivalent Se(3)Ho5 trigonal bipyramids, and edges with three equivalent Se(4)Ho5 trigonal bipyramids. In the fourth Se site, Se(4) is bonded to one Ho(1), two equivalent Ho(2), and two equivalent Ho(3) atoms to form distorted SeHo5 trigonal bipyramids that share corners with four equivalent Se(6)Ho4 tetrahedra, corners with two equivalent Se(2)Ho3Cd2 trigonal bipyramids, corners with two equivalent Se(1)Ho4Cd trigonal bipyramids, corners with two equivalent Se(3)Ho5 trigonal bipyramids,  an edgeedge with one Se(6)Ho4 tetrahedra, edges with two equivalent Se(5)Ho3Cd tetrahedra,  an edgeedge with one Se(1)Ho4Cd trigonal bipyramid, edges with two equivalent Se(4)Ho5 trigonal bipyramids, and edges with three equivalent Se(3)Ho5 trigonal bipyramids. In the fifth Se site, Se(5) is bonded to one Ho(3), two equivalent Ho(1), and one Cd(1) atom to form distorted SeHo3Cd tetrahedra that share  a cornercorner with one Se(6)Ho4 tetrahedra, corners with two equivalent Se(5)Ho3Cd tetrahedra,  a cornercorner with one Se(1)Ho4Cd trigonal bipyramid, corners with four equivalent Se(2)Ho3Cd2 trigonal bipyramids, corners with four equivalent Se(3)Ho5 trigonal bipyramids,  an edgeedge with one Se(2)Ho3Cd2 trigonal bipyramid,  an edgeedge with one Se(3)Ho5 trigonal bipyramid, and edges with two equivalent Se(4)Ho5 trigonal bipyramids. In the sixth Se site, Se(6) is bonded to one Ho(3), one Ho(4), and two equivalent Ho(2) atoms to form SeHo4 tetrahedra that share  a cornercorner with one Se(5)Ho3Cd tetrahedra, corners with two equivalent Se(6)Ho4 tetrahedra,  a cornercorner with one Se(2)Ho3Cd2 trigonal bipyramid, corners with four equivalent Se(1)Ho4Cd trigonal bipyramids, corners with four equivalent Se(4)Ho5 trigonal bipyramids,  an edgeedge with one Se(1)Ho4Cd trigonal bipyramid,  an edgeedge with one Se(4)Ho5 trigonal bipyramid, and edges with two equivalent Se(3)Ho5 trigonal bipyramids. In the seventh Se site, Se(7) is bonded in a square co-planar geometry to two equivalent Ho(4) and two equivalent Cd(1) atoms.
Ho4CdSe7 crystallizes in the monoclinic Cm space group. There are four inequivalent Ho sites. In the first Ho site, Ho(1) is bonded in a 7-coordinate geometry to one Se(4), two equivalent Se(2), two equivalent Se(3), and two equivalent Se(5) atoms. The Ho(1)-Se(4) bond length is 3.18 Å. Both Ho(1)-Se(2) bond lengths are 2.98 Å. Both Ho(1)-Se(3) bond lengths are 3.03 Å. Both Ho(1)-Se(5) bond lengths are 2.84 Å. In the second Ho site, Ho(2) is bonded in a 7-coordinate geometry to one Se(3), two equivalent Se(1), two equivalent Se(4), and two equivalent Se(6) atoms. The Ho(2)-Se(3) bond length is 3.11 Å. Both Ho(2)-Se(1) bond lengths are 3.03 Å. Both Ho(2)-Se(4) bond lengths are 3.01 Å. Both Ho(2)-Se(6) bond lengths are 2.84 Å. In the third Ho site, Ho(3) is bonded to one Se(5), one Se(6), two equivalent Se(3), and two equivalent Se(4) atoms to form HoSe6 octahedra that share  a cornercorner with one Ho(4)Se6 octahedra,  a cornercorner with one Cd(1)Se6 octahedra, and edges with two equivalent Ho(3)Se6 octahedra. The corner-sharing octahedral tilt angles range from 54-56°. The Ho(3)-Se(5) bond length is 2.79 Å. The Ho(3)-Se(6) bond length is 2.81 Å. Both Ho(3)-Se(3) bond lengths are 2.87 Å. Both Ho(3)-Se(4) bond lengths are 2.87 Å. In the fourth Ho site, Ho(4) is bonded to one Se(2), one Se(6), two equivalent Se(1), and two equivalent Se(7) atoms to form HoSe6 octahedra that share  a cornercorner with one Ho(3)Se6 octahedra, corners with two equivalent Cd(1)Se6 octahedra, edges with two equivalent Ho(4)Se6 octahedra, and edges with three equivalent Cd(1)Se6 octahedra. The corner-sharing octahedral tilt angles range from 3-54°. The Ho(4)-Se(2) bond length is 2.85 Å. The Ho(4)-Se(6) bond length is 2.86 Å. Both Ho(4)-Se(1) bond lengths are 2.91 Å. Both Ho(4)-Se(7) bond lengths are 2.77 Å. Cd(1) is bonded to one Se(1), one Se(5), two equivalent Se(2), and two equivalent Se(7) atoms to form CdSe6 octahedra that share  a cornercorner with one Ho(3)Se6 octahedra, corners with two equivalent Ho(4)Se6 octahedra, edges with two equivalent Cd(1)Se6 octahedra, and edges with three equivalent Ho(4)Se6 octahedra. The corner-sharing octahedral tilt angles range from 3-56°. The Cd(1)-Se(1) bond length is 2.89 Å. The Cd(1)-Se(5) bond length is 2.77 Å. Both Cd(1)-Se(2) bond lengths are 2.88 Å. Both Cd(1)-Se(7) bond lengths are 2.84 Å. There are seven inequivalent Se sites. In the first Se site, Se(1) is bonded to two equivalent Ho(2), two equivalent Ho(4), and one Cd(1) atom to form SeHo4Cd trigonal bipyramids that share  a cornercorner with one Se(5)Ho3Cd tetrahedra, corners with four equivalent Se(6)Ho4 tetrahedra, corners with two equivalent Se(3)Ho5 trigonal bipyramids, corners with two equivalent Se(4)Ho5 trigonal bipyramids,  an edgeedge with one Se(6)Ho4 tetrahedra,  an edgeedge with one Se(4)Ho5 trigonal bipyramid, edges with two equivalent Se(2)Ho3Cd2 trigonal bipyramids, and edges with two equivalent Se(1)Ho4Cd trigonal bipyramids. In the second Se site, Se(2) is bonded to one Ho(4), two equivalent Ho(1), and two equivalent Cd(1) atoms to form SeHo3Cd2 trigonal bipyramids that share  a cornercorner with one Se(6)Ho4 tetrahedra, corners with four equivalent Se(5)Ho3Cd tetrahedra, corners with two equivalent Se(3)Ho5 trigonal bipyramids, corners with two equivalent Se(4)Ho5 trigonal bipyramids,  an edgeedge with one Se(5)Ho3Cd tetrahedra,  an edgeedge with one Se(3)Ho5 trigonal bipyramid, edges with two equivalent Se(2)Ho3Cd2 trigonal bipyramids, and edges with two equivalent Se(1)Ho4Cd trigonal bipyramids. In the third Se site, Se(3) is bonded to one Ho(2), two equivalent Ho(1), and two equivalent Ho(3) atoms to form distorted SeHo5 trigonal bipyramids that share corners with four equivalent Se(5)Ho3Cd tetrahedra, corners with two equivalent Se(2)Ho3Cd2 trigonal bipyramids, corners with two equivalent Se(1)Ho4Cd trigonal bipyramids, corners with two equivalent Se(4)Ho5 trigonal bipyramids,  an edgeedge with one Se(5)Ho3Cd tetrahedra, edges with two equivalent Se(6)Ho4 tetrahedra,  an edgeedge with one Se(2)Ho3Cd2 trigonal bipyramid, edges with two equivalent Se(3)Ho5 trigonal bipyramids, and edges with three equivalent Se(4)Ho5 trigonal bipyramids. In the fourth Se site, Se(4) is bonded to one Ho(1), two equivalent Ho(2), and two equivalent Ho(3) atoms to form distorted SeHo5 trigonal bipyramids that share corners with four equivalent Se(6)Ho4 tetrahedra, corners with two equivalent Se(2)Ho3Cd2 trigonal bipyramids, corners with two equivalent Se(1)Ho4Cd trigonal bipyramids, corners with two equivalent Se(3)Ho5 trigonal bipyramids,  an edgeedge with one Se(6)Ho4 tetrahedra, edges with two equivalent Se(5)Ho3Cd tetrahedra,  an edgeedge with one Se(1)Ho4Cd trigonal bipyramid, edges with two equivalent Se(4)Ho5 trigonal bipyramids, and edges with three equivalent Se(3)Ho5 trigonal bipyramids. In the fifth Se site, Se(5) is bonded to one Ho(3), two equivalent Ho(1), and one Cd(1) atom to form distorted SeHo3Cd tetrahedra that share  a cornercorner with one Se(6)Ho4 tetrahedra, corners with two equivalent Se(5)Ho3Cd tetrahedra,  a cornercorner with one Se(1)Ho4Cd trigonal bipyramid, corners with four equivalent Se(2)Ho3Cd2 trigonal bipyramids, corners with four equivalent Se(3)Ho5 trigonal bipyramids,  an edgeedge with one Se(2)Ho3Cd2 trigonal bipyramid,  an edgeedge with one Se(3)Ho5 trigonal bipyramid, and edges with two equivalent Se(4)Ho5 trigonal bipyramids. In the sixth Se site, Se(6) is bonded to one Ho(3), one Ho(4), and two equivalent Ho(2) atoms to form SeHo4 tetrahedra that share  a cornercorner with one Se(5)Ho3Cd tetrahedra, corners with two equivalent Se(6)Ho4 tetrahedra,  a cornercorner with one Se(2)Ho3Cd2 trigonal bipyramid, corners with four equivalent Se(1)Ho4Cd trigonal bipyramids, corners with four equivalent Se(4)Ho5 trigonal bipyramids,  an edgeedge with one Se(1)Ho4Cd trigonal bipyramid,  an edgeedge with one Se(4)Ho5 trigonal bipyramid, and edges with two equivalent Se(3)Ho5 trigonal bipyramids. In the seventh Se site, Se(7) is bonded in a square co-planar geometry to two equivalent Ho(4) and two equivalent Cd(1) atoms.