UEr4S7 crystallizes in the monoclinic Cm space group. U(1) is bonded to one S(1), one S(5), two equivalent S(6), and two equivalent S(7) atoms to form US6 octahedra that share  a cornercorner with one Er(4)S6 octahedra, corners with two equivalent Er(3)S6 octahedra, corners with two equivalent Er(2)S7 pentagonal bipyramids, corners with four equivalent Er(1)S7 pentagonal bipyramids, edges with two equivalent U(1)S6 octahedra, edges with three equivalent Er(3)S6 octahedra, and  an edgeedge with one Er(1)S7 pentagonal bipyramid. The corner-sharing octahedral tilt angles range from 1-56°. There are four inequivalent Er sites. In the first Er site, Er(1) is bonded to one S(4), two equivalent S(1), two equivalent S(3), and two equivalent S(6) atoms to form distorted ErS7 pentagonal bipyramids that share corners with two equivalent Er(3)S6 octahedra, corners with two equivalent Er(4)S6 octahedra, corners with four equivalent U(1)S6 octahedra,  an edgeedge with one U(1)S6 octahedra, edges with three equivalent Er(4)S6 octahedra, edges with two equivalent Er(2)S7 pentagonal bipyramids, and faces with two equivalent Er(1)S7 pentagonal bipyramids. The corner-sharing octahedral tilt angles range from 22-65°. In the second Er site, Er(2) is bonded to one S(3), two equivalent S(2), two equivalent S(4), and two equivalent S(5) atoms to form distorted ErS7 pentagonal bipyramids that share corners with two equivalent U(1)S6 octahedra, corners with two equivalent Er(4)S6 octahedra, corners with four equivalent Er(3)S6 octahedra,  an edgeedge with one Er(3)S6 octahedra, edges with three equivalent Er(4)S6 octahedra, edges with two equivalent Er(1)S7 pentagonal bipyramids, and faces with two equivalent Er(2)S7 pentagonal bipyramids. The corner-sharing octahedral tilt angles range from 22-68°. In the third Er site, Er(3) is bonded to one S(2), one S(6), two equivalent S(5), and two equivalent S(7) atoms to form ErS6 octahedra that share  a cornercorner with one Er(4)S6 octahedra, corners with two equivalent U(1)S6 octahedra, corners with two equivalent Er(1)S7 pentagonal bipyramids, corners with four equivalent Er(2)S7 pentagonal bipyramids, edges with two equivalent Er(3)S6 octahedra, edges with three equivalent U(1)S6 octahedra, and  an edgeedge with one Er(2)S7 pentagonal bipyramid. The corner-sharing octahedral tilt angles range from 1-57°. In the fourth Er site, Er(4) is bonded to one S(1), one S(2), two equivalent S(3), and two equivalent S(4) atoms to form ErS6 octahedra that share  a cornercorner with one U(1)S6 octahedra,  a cornercorner with one Er(3)S6 octahedra, corners with two equivalent Er(1)S7 pentagonal bipyramids, corners with two equivalent Er(2)S7 pentagonal bipyramids, edges with two equivalent Er(4)S6 octahedra, edges with three equivalent Er(1)S7 pentagonal bipyramids, and edges with three equivalent Er(2)S7 pentagonal bipyramids. The corner-sharing octahedral tilt angles range from 56-57°. There are seven inequivalent S sites. In the first S site, S(1) is bonded to one U(1), one Er(4), and two equivalent Er(1) atoms to form distorted SEr3U tetrahedra that share  a cornercorner with one S(2)Er4 tetrahedra, corners with two equivalent S(1)Er3U tetrahedra,  a cornercorner with one S(5)Er4U trigonal bipyramid, corners with four equivalent S(6)Er3U2 trigonal bipyramids, corners with four equivalent S(3)Er5 trigonal bipyramids,  an edgeedge with one S(6)Er3U2 trigonal bipyramid,  an edgeedge with one S(3)Er5 trigonal bipyramid, and edges with two equivalent S(4)Er5 trigonal bipyramids. In the second S site, S(2) is bonded to one Er(3), one Er(4), and two equivalent Er(2) atoms to form distorted SEr4 tetrahedra that share  a cornercorner with one S(1)Er3U tetrahedra, corners with two equivalent S(2)Er4 tetrahedra,  a cornercorner with one S(6)Er3U2 trigonal bipyramid, corners with four equivalent S(5)Er4U trigonal bipyramids, corners with four equivalent S(4)Er5 trigonal bipyramids,  an edgeedge with one S(5)Er4U trigonal bipyramid,  an edgeedge with one S(4)Er5 trigonal bipyramid, and edges with two equivalent S(3)Er5 trigonal bipyramids. In the third S site, S(3) is bonded to one Er(2), two equivalent Er(1), and two equivalent Er(4) atoms to form distorted SEr5 trigonal bipyramids that share corners with four equivalent S(1)Er3U tetrahedra, corners with two equivalent S(6)Er3U2 trigonal bipyramids, corners with two equivalent S(5)Er4U trigonal bipyramids, corners with two equivalent S(4)Er5 trigonal bipyramids,  an edgeedge with one S(1)Er3U tetrahedra, edges with two equivalent S(2)Er4 tetrahedra,  an edgeedge with one S(6)Er3U2 trigonal bipyramid, edges with two equivalent S(3)Er5 trigonal bipyramids, and edges with three equivalent S(4)Er5 trigonal bipyramids. In the fourth S site, S(4) is bonded to one Er(1), two equivalent Er(2), and two equivalent Er(4) atoms to form distorted SEr5 trigonal bipyramids that share corners with four equivalent S(2)Er4 tetrahedra, corners with two equivalent S(6)Er3U2 trigonal bipyramids, corners with two equivalent S(5)Er4U trigonal bipyramids, corners with two equivalent S(3)Er5 trigonal bipyramids,  an edgeedge with one S(2)Er4 tetrahedra, edges with two equivalent S(1)Er3U tetrahedra,  an edgeedge with one S(5)Er4U trigonal bipyramid, edges with two equivalent S(4)Er5 trigonal bipyramids, and edges with three equivalent S(3)Er5 trigonal bipyramids. In the fifth S site, S(5) is bonded to one U(1), two equivalent Er(2), and two equivalent Er(3) atoms to form SEr4U trigonal bipyramids that share  a cornercorner with one S(1)Er3U tetrahedra, corners with four equivalent S(2)Er4 tetrahedra, corners with two equivalent S(3)Er5 trigonal bipyramids, corners with two equivalent S(4)Er5 trigonal bipyramids,  an edgeedge with one S(2)Er4 tetrahedra,  an edgeedge with one S(4)Er5 trigonal bipyramid, edges with two equivalent S(6)Er3U2 trigonal bipyramids, and edges with two equivalent S(5)Er4U trigonal bipyramids. In the sixth S site, S(6) is bonded to two equivalent U(1), one Er(3), and two equivalent Er(1) atoms to form SEr3U2 trigonal bipyramids that share  a cornercorner with one S(2)Er4 tetrahedra, corners with four equivalent S(1)Er3U tetrahedra, corners with two equivalent S(3)Er5 trigonal bipyramids, corners with two equivalent S(4)Er5 trigonal bipyramids,  an edgeedge with one S(1)Er3U tetrahedra,  an edgeedge with one S(3)Er5 trigonal bipyramid, edges with two equivalent S(6)Er3U2 trigonal bipyramids, and edges with two equivalent S(5)Er4U trigonal bipyramids. In the seventh S site, S(7) is bonded in a rectangular see-saw-like geometry to two equivalent U(1) and two equivalent Er(3) atoms.
UEr4S7 crystallizes in the monoclinic Cm space group. U(1) is bonded to one S(1), one S(5), two equivalent S(6), and two equivalent S(7) atoms to form US6 octahedra that share  a cornercorner with one Er(4)S6 octahedra, corners with two equivalent Er(3)S6 octahedra, corners with two equivalent Er(2)S7 pentagonal bipyramids, corners with four equivalent Er(1)S7 pentagonal bipyramids, edges with two equivalent U(1)S6 octahedra, edges with three equivalent Er(3)S6 octahedra, and  an edgeedge with one Er(1)S7 pentagonal bipyramid. The corner-sharing octahedral tilt angles range from 1-56°. The U(1)-S(1) bond length is 2.72 Å. The U(1)-S(5) bond length is 2.81 Å. Both U(1)-S(6) bond lengths are 2.78 Å. Both U(1)-S(7) bond lengths are 2.70 Å. There are four inequivalent Er sites. In the first Er site, Er(1) is bonded to one S(4), two equivalent S(1), two equivalent S(3), and two equivalent S(6) atoms to form distorted ErS7 pentagonal bipyramids that share corners with two equivalent Er(3)S6 octahedra, corners with two equivalent Er(4)S6 octahedra, corners with four equivalent U(1)S6 octahedra,  an edgeedge with one U(1)S6 octahedra, edges with three equivalent Er(4)S6 octahedra, edges with two equivalent Er(2)S7 pentagonal bipyramids, and faces with two equivalent Er(1)S7 pentagonal bipyramids. The corner-sharing octahedral tilt angles range from 22-65°. The Er(1)-S(4) bond length is 2.93 Å. Both Er(1)-S(1) bond lengths are 2.72 Å. Both Er(1)-S(3) bond lengths are 2.79 Å. Both Er(1)-S(6) bond lengths are 2.86 Å. In the second Er site, Er(2) is bonded to one S(3), two equivalent S(2), two equivalent S(4), and two equivalent S(5) atoms to form distorted ErS7 pentagonal bipyramids that share corners with two equivalent U(1)S6 octahedra, corners with two equivalent Er(4)S6 octahedra, corners with four equivalent Er(3)S6 octahedra,  an edgeedge with one Er(3)S6 octahedra, edges with three equivalent Er(4)S6 octahedra, edges with two equivalent Er(1)S7 pentagonal bipyramids, and faces with two equivalent Er(2)S7 pentagonal bipyramids. The corner-sharing octahedral tilt angles range from 22-68°. The Er(2)-S(3) bond length is 2.94 Å. Both Er(2)-S(2) bond lengths are 2.71 Å. Both Er(2)-S(4) bond lengths are 2.80 Å. Both Er(2)-S(5) bond lengths are 2.88 Å. In the third Er site, Er(3) is bonded to one S(2), one S(6), two equivalent S(5), and two equivalent S(7) atoms to form ErS6 octahedra that share  a cornercorner with one Er(4)S6 octahedra, corners with two equivalent U(1)S6 octahedra, corners with two equivalent Er(1)S7 pentagonal bipyramids, corners with four equivalent Er(2)S7 pentagonal bipyramids, edges with two equivalent Er(3)S6 octahedra, edges with three equivalent U(1)S6 octahedra, and  an edgeedge with one Er(2)S7 pentagonal bipyramid. The corner-sharing octahedral tilt angles range from 1-57°. The Er(3)-S(2) bond length is 2.70 Å. The Er(3)-S(6) bond length is 2.77 Å. Both Er(3)-S(5) bond lengths are 2.72 Å. Both Er(3)-S(7) bond lengths are 2.66 Å. In the fourth Er site, Er(4) is bonded to one S(1), one S(2), two equivalent S(3), and two equivalent S(4) atoms to form ErS6 octahedra that share  a cornercorner with one U(1)S6 octahedra,  a cornercorner with one Er(3)S6 octahedra, corners with two equivalent Er(1)S7 pentagonal bipyramids, corners with two equivalent Er(2)S7 pentagonal bipyramids, edges with two equivalent Er(4)S6 octahedra, edges with three equivalent Er(1)S7 pentagonal bipyramids, and edges with three equivalent Er(2)S7 pentagonal bipyramids. The corner-sharing octahedral tilt angles range from 56-57°. The Er(4)-S(1) bond length is 2.67 Å. The Er(4)-S(2) bond length is 2.65 Å. Both Er(4)-S(3) bond lengths are 2.71 Å. Both Er(4)-S(4) bond lengths are 2.72 Å. There are seven inequivalent S sites. In the first S site, S(1) is bonded to one U(1), one Er(4), and two equivalent Er(1) atoms to form distorted SEr3U tetrahedra that share  a cornercorner with one S(2)Er4 tetrahedra, corners with two equivalent S(1)Er3U tetrahedra,  a cornercorner with one S(5)Er4U trigonal bipyramid, corners with four equivalent S(6)Er3U2 trigonal bipyramids, corners with four equivalent S(3)Er5 trigonal bipyramids,  an edgeedge with one S(6)Er3U2 trigonal bipyramid,  an edgeedge with one S(3)Er5 trigonal bipyramid, and edges with two equivalent S(4)Er5 trigonal bipyramids. In the second S site, S(2) is bonded to one Er(3), one Er(4), and two equivalent Er(2) atoms to form distorted SEr4 tetrahedra that share  a cornercorner with one S(1)Er3U tetrahedra, corners with two equivalent S(2)Er4 tetrahedra,  a cornercorner with one S(6)Er3U2 trigonal bipyramid, corners with four equivalent S(5)Er4U trigonal bipyramids, corners with four equivalent S(4)Er5 trigonal bipyramids,  an edgeedge with one S(5)Er4U trigonal bipyramid,  an edgeedge with one S(4)Er5 trigonal bipyramid, and edges with two equivalent S(3)Er5 trigonal bipyramids. In the third S site, S(3) is bonded to one Er(2), two equivalent Er(1), and two equivalent Er(4) atoms to form distorted SEr5 trigonal bipyramids that share corners with four equivalent S(1)Er3U tetrahedra, corners with two equivalent S(6)Er3U2 trigonal bipyramids, corners with two equivalent S(5)Er4U trigonal bipyramids, corners with two equivalent S(4)Er5 trigonal bipyramids,  an edgeedge with one S(1)Er3U tetrahedra, edges with two equivalent S(2)Er4 tetrahedra,  an edgeedge with one S(6)Er3U2 trigonal bipyramid, edges with two equivalent S(3)Er5 trigonal bipyramids, and edges with three equivalent S(4)Er5 trigonal bipyramids. In the fourth S site, S(4) is bonded to one Er(1), two equivalent Er(2), and two equivalent Er(4) atoms to form distorted SEr5 trigonal bipyramids that share corners with four equivalent S(2)Er4 tetrahedra, corners with two equivalent S(6)Er3U2 trigonal bipyramids, corners with two equivalent S(5)Er4U trigonal bipyramids, corners with two equivalent S(3)Er5 trigonal bipyramids,  an edgeedge with one S(2)Er4 tetrahedra, edges with two equivalent S(1)Er3U tetrahedra,  an edgeedge with one S(5)Er4U trigonal bipyramid, edges with two equivalent S(4)Er5 trigonal bipyramids, and edges with three equivalent S(3)Er5 trigonal bipyramids. In the fifth S site, S(5) is bonded to one U(1), two equivalent Er(2), and two equivalent Er(3) atoms to form SEr4U trigonal bipyramids that share  a cornercorner with one S(1)Er3U tetrahedra, corners with four equivalent S(2)Er4 tetrahedra, corners with two equivalent S(3)Er5 trigonal bipyramids, corners with two equivalent S(4)Er5 trigonal bipyramids,  an edgeedge with one S(2)Er4 tetrahedra,  an edgeedge with one S(4)Er5 trigonal bipyramid, edges with two equivalent S(6)Er3U2 trigonal bipyramids, and edges with two equivalent S(5)Er4U trigonal bipyramids. In the sixth S site, S(6) is bonded to two equivalent U(1), one Er(3), and two equivalent Er(1) atoms to form SEr3U2 trigonal bipyramids that share  a cornercorner with one S(2)Er4 tetrahedra, corners with four equivalent S(1)Er3U tetrahedra, corners with two equivalent S(3)Er5 trigonal bipyramids, corners with two equivalent S(4)Er5 trigonal bipyramids,  an edgeedge with one S(1)Er3U tetrahedra,  an edgeedge with one S(3)Er5 trigonal bipyramid, edges with two equivalent S(6)Er3U2 trigonal bipyramids, and edges with two equivalent S(5)Er4U trigonal bipyramids. In the seventh S site, S(7) is bonded in a rectangular see-saw-like geometry to two equivalent U(1) and two equivalent Er(3) atoms.