Dy4CrSe7 crystallizes in the monoclinic Cm space group. There are four inequivalent Dy sites. In the first Dy site, Dy(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 Dy site, Dy(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 Dy site, Dy(3) is bonded to one Se(5), one Se(6), two equivalent Se(3), and two equivalent Se(4) atoms to form DySe6 octahedra that share  a cornercorner with one Dy(4)Se6 octahedra,  a cornercorner with one Cr(1)Se6 octahedra, and edges with two equivalent Dy(3)Se6 octahedra. The corner-sharing octahedral tilt angles range from 50-54°. In the fourth Dy site, Dy(4) is bonded to one Se(2), one Se(6), two equivalent Se(1), and two equivalent Se(7) atoms to form DySe6 octahedra that share  a cornercorner with one Dy(3)Se6 octahedra, corners with two equivalent Cr(1)Se6 octahedra, edges with two equivalent Dy(4)Se6 octahedra, and edges with three equivalent Cr(1)Se6 octahedra. The corner-sharing octahedral tilt angles range from 3-50°. Cr(1) is bonded to one Se(1), one Se(5), two equivalent Se(2), and two equivalent Se(7) atoms to form CrSe6 octahedra that share  a cornercorner with one Dy(3)Se6 octahedra, corners with two equivalent Dy(4)Se6 octahedra, edges with two equivalent Cr(1)Se6 octahedra, and edges with three equivalent Dy(4)Se6 octahedra. The corner-sharing octahedral tilt angles range from 3-54°. There are seven inequivalent Se sites. In the first Se site, Se(1) is bonded to two equivalent Dy(2), two equivalent Dy(4), and one Cr(1) atom to form distorted SeDy4Cr trigonal bipyramids that share  a cornercorner with one Se(5)Dy3Cr tetrahedra, corners with four equivalent Se(6)Dy4 tetrahedra, corners with two equivalent Se(3)Dy5 trigonal bipyramids, corners with two equivalent Se(4)Dy5 trigonal bipyramids, edges with two equivalent Se(2)Dy3Cr2 square pyramids,  an edgeedge with one Se(6)Dy4 tetrahedra,  an edgeedge with one Se(4)Dy5 trigonal bipyramid, and edges with two equivalent Se(1)Dy4Cr trigonal bipyramids. In the second Se site, Se(2) is bonded to one Dy(4), two equivalent Dy(1), and two equivalent Cr(1) atoms to form SeDy3Cr2 square pyramids that share  a cornercorner with one Se(6)Dy4 tetrahedra, corners with four equivalent Se(5)Dy3Cr tetrahedra, corners with two equivalent Se(3)Dy5 trigonal bipyramids, corners with two equivalent Se(4)Dy5 trigonal bipyramids, edges with two equivalent Se(2)Dy3Cr2 square pyramids,  an edgeedge with one Se(5)Dy3Cr tetrahedra,  an edgeedge with one Se(3)Dy5 trigonal bipyramid, and edges with two equivalent Se(1)Dy4Cr trigonal bipyramids. In the third Se site, Se(3) is bonded to one Dy(2), two equivalent Dy(1), and two equivalent Dy(3) atoms to form distorted SeDy5 trigonal bipyramids that share corners with two equivalent Se(2)Dy3Cr2 square pyramids, corners with four equivalent Se(5)Dy3Cr tetrahedra, corners with two equivalent Se(1)Dy4Cr trigonal bipyramids, corners with two equivalent Se(4)Dy5 trigonal bipyramids,  an edgeedge with one Se(2)Dy3Cr2 square pyramid,  an edgeedge with one Se(5)Dy3Cr tetrahedra, edges with two equivalent Se(6)Dy4 tetrahedra, edges with two equivalent Se(3)Dy5 trigonal bipyramids, and edges with three equivalent Se(4)Dy5 trigonal bipyramids. In the fourth Se site, Se(4) is bonded to one Dy(1), two equivalent Dy(2), and two equivalent Dy(3) atoms to form distorted SeDy5 trigonal bipyramids that share corners with two equivalent Se(2)Dy3Cr2 square pyramids, corners with four equivalent Se(6)Dy4 tetrahedra, corners with two equivalent Se(1)Dy4Cr trigonal bipyramids, corners with two equivalent Se(3)Dy5 trigonal bipyramids,  an edgeedge with one Se(6)Dy4 tetrahedra, edges with two equivalent Se(5)Dy3Cr tetrahedra,  an edgeedge with one Se(1)Dy4Cr trigonal bipyramid, edges with two equivalent Se(4)Dy5 trigonal bipyramids, and edges with three equivalent Se(3)Dy5 trigonal bipyramids. In the fifth Se site, Se(5) is bonded to one Dy(3), two equivalent Dy(1), and one Cr(1) atom to form distorted SeDy3Cr tetrahedra that share corners with four equivalent Se(2)Dy3Cr2 square pyramids,  a cornercorner with one Se(6)Dy4 tetrahedra, corners with two equivalent Se(5)Dy3Cr tetrahedra,  a cornercorner with one Se(1)Dy4Cr trigonal bipyramid, corners with four equivalent Se(3)Dy5 trigonal bipyramids,  an edgeedge with one Se(2)Dy3Cr2 square pyramid,  an edgeedge with one Se(3)Dy5 trigonal bipyramid, and edges with two equivalent Se(4)Dy5 trigonal bipyramids. In the sixth Se site, Se(6) is bonded to one Dy(3), one Dy(4), and two equivalent Dy(2) atoms to form SeDy4 tetrahedra that share  a cornercorner with one Se(2)Dy3Cr2 square pyramid,  a cornercorner with one Se(5)Dy3Cr tetrahedra, corners with two equivalent Se(6)Dy4 tetrahedra, corners with four equivalent Se(1)Dy4Cr trigonal bipyramids, corners with four equivalent Se(4)Dy5 trigonal bipyramids,  an edgeedge with one Se(1)Dy4Cr trigonal bipyramid,  an edgeedge with one Se(4)Dy5 trigonal bipyramid, and edges with two equivalent Se(3)Dy5 trigonal bipyramids. In the seventh Se site, Se(7) is bonded in a rectangular see-saw-like geometry to two equivalent Dy(4) and two equivalent Cr(1) atoms.
Dy4CrSe7 crystallizes in the monoclinic Cm space group. There are four inequivalent Dy sites. In the first Dy site, Dy(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 Dy(1)-Se(4) bond length is 3.24 Å. Both Dy(1)-Se(2) bond lengths are 2.99 Å. Both Dy(1)-Se(3) bond lengths are 3.00 Å. Both Dy(1)-Se(5) bond lengths are 2.88 Å. In the second Dy site, Dy(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 Dy(2)-Se(3) bond length is 3.11 Å. Both Dy(2)-Se(1) bond lengths are 3.07 Å. Both Dy(2)-Se(4) bond lengths are 2.99 Å. Both Dy(2)-Se(6) bond lengths are 2.84 Å. In the third Dy site, Dy(3) is bonded to one Se(5), one Se(6), two equivalent Se(3), and two equivalent Se(4) atoms to form DySe6 octahedra that share  a cornercorner with one Dy(4)Se6 octahedra,  a cornercorner with one Cr(1)Se6 octahedra, and edges with two equivalent Dy(3)Se6 octahedra. The corner-sharing octahedral tilt angles range from 50-54°. The Dy(3)-Se(5) bond length is 2.81 Å. The Dy(3)-Se(6) bond length is 2.81 Å. Both Dy(3)-Se(3) bond lengths are 2.86 Å. Both Dy(3)-Se(4) bond lengths are 2.85 Å. In the fourth Dy site, Dy(4) is bonded to one Se(2), one Se(6), two equivalent Se(1), and two equivalent Se(7) atoms to form DySe6 octahedra that share  a cornercorner with one Dy(3)Se6 octahedra, corners with two equivalent Cr(1)Se6 octahedra, edges with two equivalent Dy(4)Se6 octahedra, and edges with three equivalent Cr(1)Se6 octahedra. The corner-sharing octahedral tilt angles range from 3-50°. The Dy(4)-Se(2) bond length is 2.81 Å. The Dy(4)-Se(6) bond length is 2.83 Å. Both Dy(4)-Se(1) bond lengths are 2.93 Å. Both Dy(4)-Se(7) bond lengths are 2.80 Å. Cr(1) is bonded to one Se(1), one Se(5), two equivalent Se(2), and two equivalent Se(7) atoms to form CrSe6 octahedra that share  a cornercorner with one Dy(3)Se6 octahedra, corners with two equivalent Dy(4)Se6 octahedra, edges with two equivalent Cr(1)Se6 octahedra, and edges with three equivalent Dy(4)Se6 octahedra. The corner-sharing octahedral tilt angles range from 3-54°. The Cr(1)-Se(1) bond length is 2.65 Å. The Cr(1)-Se(5) bond length is 2.57 Å. Both Cr(1)-Se(2) bond lengths are 2.74 Å. Both Cr(1)-Se(7) bond lengths are 2.69 Å. There are seven inequivalent Se sites. In the first Se site, Se(1) is bonded to two equivalent Dy(2), two equivalent Dy(4), and one Cr(1) atom to form distorted SeDy4Cr trigonal bipyramids that share  a cornercorner with one Se(5)Dy3Cr tetrahedra, corners with four equivalent Se(6)Dy4 tetrahedra, corners with two equivalent Se(3)Dy5 trigonal bipyramids, corners with two equivalent Se(4)Dy5 trigonal bipyramids, edges with two equivalent Se(2)Dy3Cr2 square pyramids,  an edgeedge with one Se(6)Dy4 tetrahedra,  an edgeedge with one Se(4)Dy5 trigonal bipyramid, and edges with two equivalent Se(1)Dy4Cr trigonal bipyramids. In the second Se site, Se(2) is bonded to one Dy(4), two equivalent Dy(1), and two equivalent Cr(1) atoms to form SeDy3Cr2 square pyramids that share  a cornercorner with one Se(6)Dy4 tetrahedra, corners with four equivalent Se(5)Dy3Cr tetrahedra, corners with two equivalent Se(3)Dy5 trigonal bipyramids, corners with two equivalent Se(4)Dy5 trigonal bipyramids, edges with two equivalent Se(2)Dy3Cr2 square pyramids,  an edgeedge with one Se(5)Dy3Cr tetrahedra,  an edgeedge with one Se(3)Dy5 trigonal bipyramid, and edges with two equivalent Se(1)Dy4Cr trigonal bipyramids. In the third Se site, Se(3) is bonded to one Dy(2), two equivalent Dy(1), and two equivalent Dy(3) atoms to form distorted SeDy5 trigonal bipyramids that share corners with two equivalent Se(2)Dy3Cr2 square pyramids, corners with four equivalent Se(5)Dy3Cr tetrahedra, corners with two equivalent Se(1)Dy4Cr trigonal bipyramids, corners with two equivalent Se(4)Dy5 trigonal bipyramids,  an edgeedge with one Se(2)Dy3Cr2 square pyramid,  an edgeedge with one Se(5)Dy3Cr tetrahedra, edges with two equivalent Se(6)Dy4 tetrahedra, edges with two equivalent Se(3)Dy5 trigonal bipyramids, and edges with three equivalent Se(4)Dy5 trigonal bipyramids. In the fourth Se site, Se(4) is bonded to one Dy(1), two equivalent Dy(2), and two equivalent Dy(3) atoms to form distorted SeDy5 trigonal bipyramids that share corners with two equivalent Se(2)Dy3Cr2 square pyramids, corners with four equivalent Se(6)Dy4 tetrahedra, corners with two equivalent Se(1)Dy4Cr trigonal bipyramids, corners with two equivalent Se(3)Dy5 trigonal bipyramids,  an edgeedge with one Se(6)Dy4 tetrahedra, edges with two equivalent Se(5)Dy3Cr tetrahedra,  an edgeedge with one Se(1)Dy4Cr trigonal bipyramid, edges with two equivalent Se(4)Dy5 trigonal bipyramids, and edges with three equivalent Se(3)Dy5 trigonal bipyramids. In the fifth Se site, Se(5) is bonded to one Dy(3), two equivalent Dy(1), and one Cr(1) atom to form distorted SeDy3Cr tetrahedra that share corners with four equivalent Se(2)Dy3Cr2 square pyramids,  a cornercorner with one Se(6)Dy4 tetrahedra, corners with two equivalent Se(5)Dy3Cr tetrahedra,  a cornercorner with one Se(1)Dy4Cr trigonal bipyramid, corners with four equivalent Se(3)Dy5 trigonal bipyramids,  an edgeedge with one Se(2)Dy3Cr2 square pyramid,  an edgeedge with one Se(3)Dy5 trigonal bipyramid, and edges with two equivalent Se(4)Dy5 trigonal bipyramids. In the sixth Se site, Se(6) is bonded to one Dy(3), one Dy(4), and two equivalent Dy(2) atoms to form SeDy4 tetrahedra that share  a cornercorner with one Se(2)Dy3Cr2 square pyramid,  a cornercorner with one Se(5)Dy3Cr tetrahedra, corners with two equivalent Se(6)Dy4 tetrahedra, corners with four equivalent Se(1)Dy4Cr trigonal bipyramids, corners with four equivalent Se(4)Dy5 trigonal bipyramids,  an edgeedge with one Se(1)Dy4Cr trigonal bipyramid,  an edgeedge with one Se(4)Dy5 trigonal bipyramid, and edges with two equivalent Se(3)Dy5 trigonal bipyramids. In the seventh Se site, Se(7) is bonded in a rectangular see-saw-like geometry to two equivalent Dy(4) and two equivalent Cr(1) atoms.