Nd4(ErS2)11 crystallizes in the monoclinic C2/m space group. There are six inequivalent Er sites. In the first Er site, Er(1) is bonded to one S(2), one S(9), two equivalent S(8), and three equivalent S(11) atoms to form distorted ErS7 pentagonal bipyramids that share  a cornercorner with one Er(4)S6 octahedra, corners with two equivalent Er(3)S6 octahedra, edges with two equivalent Er(4)S6 octahedra, and edges with four equivalent Er(1)S7 pentagonal bipyramids. The corner-sharing octahedral tilt angles range from 39-50°. In the second Er site, Er(2) is bonded to one S(4), one S(7), two equivalent S(1), and two equivalent S(10) atoms to form a mixture of edge and corner-sharing ErS6 octahedra. The corner-sharing octahedral tilt angles range from 48-59°. In the third Er site, Er(3) is bonded to one S(3), one S(6), two equivalent S(5), and two equivalent S(9) atoms to form ErS6 octahedra that share corners with three equivalent Er(4)S6 octahedra, corners with two equivalent Er(1)S7 pentagonal bipyramids, edges with two equivalent Er(3)S6 octahedra, and edges with two equivalent Er(5)S6 octahedra. The corner-sharing octahedral tilt angles range from 52-62°. In the fourth Er site, Er(4) is bonded to one S(11), two equivalent S(2), and three equivalent S(3) atoms to form ErS6 octahedra that share corners with three equivalent Er(3)S6 octahedra,  a cornercorner with one Er(1)S7 pentagonal bipyramid, edges with four equivalent Er(4)S6 octahedra, and edges with two equivalent Er(1)S7 pentagonal bipyramids. The corner-sharing octahedral tilt angles range from 52-62°. In the fifth Er site, Er(5) is bonded to one S(10), one S(5), two equivalent S(4), and two equivalent S(6) atoms to form a mixture of edge and corner-sharing ErS6 octahedra. The corner-sharing octahedral tilt angles range from 48-59°. In the sixth Er site, Er(6) is bonded to two equivalent S(10) and four equivalent S(7) atoms to form a mixture of edge and corner-sharing ErS6 octahedra. The corner-sharing octahedral tilt angles are 55°. There are two inequivalent Nd sites. In the first Nd site, Nd(1) is bonded in a 8-coordinate geometry to one S(1), one S(9), two equivalent S(6), two equivalent S(7), and two equivalent S(8) atoms. In the second Nd site, Nd(2) is bonded in a 8-coordinate geometry to one S(4), one S(8), two equivalent S(1), two equivalent S(2), and two equivalent S(5) atoms. There are eleven inequivalent S sites. In the first S site, S(1) is bonded to two equivalent Er(2), one Nd(1), and two equivalent Nd(2) atoms to form distorted SNd3Er2 trigonal bipyramids that share corners with two equivalent S(6)Nd2Er3 square pyramids, corners with two equivalent S(2)Nd2Er3 trigonal bipyramids, corners with two equivalent S(5)Nd2Er3 trigonal bipyramids,  a cornercorner with one S(9)NdEr3 trigonal pyramid, edges with two equivalent S(7)Nd2Er3 square pyramids,  an edgeedge with one S(2)Nd2Er3 trigonal bipyramid,  an edgeedge with one S(5)Nd2Er3 trigonal bipyramid, edges with two equivalent S(1)Nd3Er2 trigonal bipyramids, and edges with two equivalent S(8)Nd3Er2 trigonal bipyramids. In the second S site, S(2) is bonded to one Er(1), two equivalent Er(4), and two equivalent Nd(2) atoms to form SNd2Er3 trigonal bipyramids that share corners with two equivalent S(5)Nd2Er3 trigonal bipyramids, corners with two equivalent S(1)Nd3Er2 trigonal bipyramids,  a cornercorner with one S(11)Er4 trigonal pyramid,  a cornercorner with one S(9)NdEr3 trigonal pyramid,  an edgeedge with one S(5)Nd2Er3 trigonal bipyramid,  an edgeedge with one S(1)Nd3Er2 trigonal bipyramid, edges with two equivalent S(2)Nd2Er3 trigonal bipyramids, edges with two equivalent S(8)Nd3Er2 trigonal bipyramids, and edges with two equivalent S(11)Er4 trigonal pyramids. In the third S site, S(3) is bonded in a rectangular see-saw-like geometry to one Er(3) and three equivalent Er(4) atoms. In the fourth S site, S(4) is bonded in a 3-coordinate geometry to one Er(2), two equivalent Er(5), and one Nd(2) atom. In the fifth S site, S(5) is bonded to one Er(5), two equivalent Er(3), and two equivalent Nd(2) atoms to form SNd2Er3 trigonal bipyramids that share corners with two equivalent S(2)Nd2Er3 trigonal bipyramids, corners with two equivalent S(1)Nd3Er2 trigonal bipyramids, corners with two equivalent S(8)Nd3Er2 trigonal bipyramids, corners with two equivalent S(9)NdEr3 trigonal pyramids, edges with two equivalent S(6)Nd2Er3 square pyramids,  an edgeedge with one S(2)Nd2Er3 trigonal bipyramid,  an edgeedge with one S(1)Nd3Er2 trigonal bipyramid, edges with two equivalent S(5)Nd2Er3 trigonal bipyramids, and  an edgeedge with one S(9)NdEr3 trigonal pyramid. In the sixth S site, S(6) is bonded to one Er(3), two equivalent Er(5), and two equivalent Nd(1) atoms to form SNd2Er3 square pyramids that share corners with two equivalent S(7)Nd2Er3 square pyramids, corners with two equivalent S(1)Nd3Er2 trigonal bipyramids, corners with two equivalent S(8)Nd3Er2 trigonal bipyramids,  an edgeedge with one S(7)Nd2Er3 square pyramid, edges with two equivalent S(6)Nd2Er3 square pyramids,  an edgeedge with one S(8)Nd3Er2 trigonal bipyramid, edges with two equivalent S(5)Nd2Er3 trigonal bipyramids, and edges with two equivalent S(9)NdEr3 trigonal pyramids. In the seventh S site, S(7) is bonded to one Er(2), two equivalent Er(6), and two equivalent Nd(1) atoms to form SNd2Er3 square pyramids that share corners with two equivalent S(6)Nd2Er3 square pyramids, corners with two equivalent S(7)Nd2Er3 square pyramids, corners with two equivalent S(8)Nd3Er2 trigonal bipyramids, corners with two equivalent S(9)NdEr3 trigonal pyramids,  an edgeedge with one S(6)Nd2Er3 square pyramid, edges with three equivalent S(7)Nd2Er3 square pyramids,  an edgeedge with one S(8)Nd3Er2 trigonal bipyramid, and edges with two equivalent S(1)Nd3Er2 trigonal bipyramids. In the eighth S site, S(8) is bonded to two equivalent Er(1), one Nd(2), and two equivalent Nd(1) atoms to form distorted SNd3Er2 trigonal bipyramids that share corners with two equivalent S(6)Nd2Er3 square pyramids, corners with two equivalent S(7)Nd2Er3 square pyramids, corners with two equivalent S(5)Nd2Er3 trigonal bipyramids, corners with four equivalent S(11)Er4 trigonal pyramids,  an edgeedge with one S(6)Nd2Er3 square pyramid,  an edgeedge with one S(7)Nd2Er3 square pyramid, edges with two equivalent S(2)Nd2Er3 trigonal bipyramids, edges with two equivalent S(1)Nd3Er2 trigonal bipyramids, edges with two equivalent S(8)Nd3Er2 trigonal bipyramids,  an edgeedge with one S(11)Er4 trigonal pyramid, and edges with two equivalent S(9)NdEr3 trigonal pyramids. In the ninth S site, S(9) is bonded to one Er(1), two equivalent Er(3), and one Nd(1) atom to form distorted SNdEr3 trigonal pyramids that share corners with two equivalent S(7)Nd2Er3 square pyramids,  a cornercorner with one S(2)Nd2Er3 trigonal bipyramid,  a cornercorner with one S(1)Nd3Er2 trigonal bipyramid, corners with two equivalent S(5)Nd2Er3 trigonal bipyramids, corners with two equivalent S(9)NdEr3 trigonal pyramids, corners with three equivalent S(11)Er4 trigonal pyramids, edges with two equivalent S(6)Nd2Er3 square pyramids,  an edgeedge with one S(5)Nd2Er3 trigonal bipyramid, and edges with two equivalent S(8)Nd3Er2 trigonal bipyramids. In the tenth S site, S(10) is bonded in a rectangular see-saw-like geometry to one Er(5), one Er(6), and two equivalent Er(2) atoms. In the eleventh S site, S(11) is bonded to one Er(4) and three equivalent Er(1) atoms to form distorted SEr4 trigonal pyramids that share  a cornercorner with one S(2)Nd2Er3 trigonal bipyramid, corners with four equivalent S(8)Nd3Er2 trigonal bipyramids, corners with two equivalent S(11)Er4 trigonal pyramids, corners with three equivalent S(9)NdEr3 trigonal pyramids,  an edgeedge with one S(8)Nd3Er2 trigonal bipyramid, edges with two equivalent S(2)Nd2Er3 trigonal bipyramids, and edges with two equivalent S(11)Er4 trigonal pyramids.
Nd4(ErS2)11 crystallizes in the monoclinic C2/m space group. There are six inequivalent Er sites. In the first Er site, Er(1) is bonded to one S(2), one S(9), two equivalent S(8), and three equivalent S(11) atoms to form distorted ErS7 pentagonal bipyramids that share  a cornercorner with one Er(4)S6 octahedra, corners with two equivalent Er(3)S6 octahedra, edges with two equivalent Er(4)S6 octahedra, and edges with four equivalent Er(1)S7 pentagonal bipyramids. The corner-sharing octahedral tilt angles range from 39-50°. The Er(1)-S(2) bond length is 2.87 Å. The Er(1)-S(9) bond length is 2.74 Å. Both Er(1)-S(8) bond lengths are 2.88 Å. There are two shorter (2.69 Å) and one longer (2.86 Å) Er(1)-S(11) bond length. In the second Er site, Er(2) is bonded to one S(4), one S(7), two equivalent S(1), and two equivalent S(10) atoms to form a mixture of edge and corner-sharing ErS6 octahedra. The corner-sharing octahedral tilt angles range from 48-59°. The Er(2)-S(4) bond length is 2.63 Å. The Er(2)-S(7) bond length is 2.74 Å. Both Er(2)-S(1) bond lengths are 2.77 Å. Both Er(2)-S(10) bond lengths are 2.70 Å. In the third Er site, Er(3) is bonded to one S(3), one S(6), two equivalent S(5), and two equivalent S(9) atoms to form ErS6 octahedra that share corners with three equivalent Er(4)S6 octahedra, corners with two equivalent Er(1)S7 pentagonal bipyramids, edges with two equivalent Er(3)S6 octahedra, and edges with two equivalent Er(5)S6 octahedra. The corner-sharing octahedral tilt angles range from 52-62°. The Er(3)-S(3) bond length is 2.70 Å. The Er(3)-S(6) bond length is 2.71 Å. Both Er(3)-S(5) bond lengths are 2.79 Å. Both Er(3)-S(9) bond lengths are 2.65 Å. In the fourth Er site, Er(4) is bonded to one S(11), two equivalent S(2), and three equivalent S(3) atoms to form ErS6 octahedra that share corners with three equivalent Er(3)S6 octahedra,  a cornercorner with one Er(1)S7 pentagonal bipyramid, edges with four equivalent Er(4)S6 octahedra, and edges with two equivalent Er(1)S7 pentagonal bipyramids. The corner-sharing octahedral tilt angles range from 52-62°. The Er(4)-S(11) bond length is 2.65 Å. Both Er(4)-S(2) bond lengths are 2.76 Å. There are two shorter (2.71 Å) and one longer (2.76 Å) Er(4)-S(3) bond length. In the fifth Er site, Er(5) is bonded to one S(10), one S(5), two equivalent S(4), and two equivalent S(6) atoms to form a mixture of edge and corner-sharing ErS6 octahedra. The corner-sharing octahedral tilt angles range from 48-59°. The Er(5)-S(10) bond length is 2.74 Å. The Er(5)-S(5) bond length is 2.74 Å. Both Er(5)-S(4) bond lengths are 2.64 Å. Both Er(5)-S(6) bond lengths are 2.76 Å. In the sixth Er site, Er(6) is bonded to two equivalent S(10) and four equivalent S(7) atoms to form a mixture of edge and corner-sharing ErS6 octahedra. The corner-sharing octahedral tilt angles are 55°. Both Er(6)-S(10) bond lengths are 2.72 Å. All Er(6)-S(7) bond lengths are 2.73 Å. There are two inequivalent Nd sites. In the first Nd site, Nd(1) is bonded in a 8-coordinate geometry to one S(1), one S(9), two equivalent S(6), two equivalent S(7), and two equivalent S(8) atoms. The Nd(1)-S(1) bond length is 3.00 Å. The Nd(1)-S(9) bond length is 2.92 Å. Both Nd(1)-S(6) bond lengths are 3.04 Å. Both Nd(1)-S(7) bond lengths are 3.01 Å. Both Nd(1)-S(8) bond lengths are 2.90 Å. In the second Nd site, Nd(2) is bonded in a 8-coordinate geometry to one S(4), one S(8), two equivalent S(1), two equivalent S(2), and two equivalent S(5) atoms. The Nd(2)-S(4) bond length is 3.47 Å. The Nd(2)-S(8) bond length is 2.95 Å. Both Nd(2)-S(1) bond lengths are 2.89 Å. Both Nd(2)-S(2) bond lengths are 2.96 Å. Both Nd(2)-S(5) bond lengths are 2.99 Å. There are eleven inequivalent S sites. In the first S site, S(1) is bonded to two equivalent Er(2), one Nd(1), and two equivalent Nd(2) atoms to form distorted SNd3Er2 trigonal bipyramids that share corners with two equivalent S(6)Nd2Er3 square pyramids, corners with two equivalent S(2)Nd2Er3 trigonal bipyramids, corners with two equivalent S(5)Nd2Er3 trigonal bipyramids,  a cornercorner with one S(9)NdEr3 trigonal pyramid, edges with two equivalent S(7)Nd2Er3 square pyramids,  an edgeedge with one S(2)Nd2Er3 trigonal bipyramid,  an edgeedge with one S(5)Nd2Er3 trigonal bipyramid, edges with two equivalent S(1)Nd3Er2 trigonal bipyramids, and edges with two equivalent S(8)Nd3Er2 trigonal bipyramids. In the second S site, S(2) is bonded to one Er(1), two equivalent Er(4), and two equivalent Nd(2) atoms to form SNd2Er3 trigonal bipyramids that share corners with two equivalent S(5)Nd2Er3 trigonal bipyramids, corners with two equivalent S(1)Nd3Er2 trigonal bipyramids,  a cornercorner with one S(11)Er4 trigonal pyramid,  a cornercorner with one S(9)NdEr3 trigonal pyramid,  an edgeedge with one S(5)Nd2Er3 trigonal bipyramid,  an edgeedge with one S(1)Nd3Er2 trigonal bipyramid, edges with two equivalent S(2)Nd2Er3 trigonal bipyramids, edges with two equivalent S(8)Nd3Er2 trigonal bipyramids, and edges with two equivalent S(11)Er4 trigonal pyramids. In the third S site, S(3) is bonded in a rectangular see-saw-like geometry to one Er(3) and three equivalent Er(4) atoms. In the fourth S site, S(4) is bonded in a 3-coordinate geometry to one Er(2), two equivalent Er(5), and one Nd(2) atom. In the fifth S site, S(5) is bonded to one Er(5), two equivalent Er(3), and two equivalent Nd(2) atoms to form SNd2Er3 trigonal bipyramids that share corners with two equivalent S(2)Nd2Er3 trigonal bipyramids, corners with two equivalent S(1)Nd3Er2 trigonal bipyramids, corners with two equivalent S(8)Nd3Er2 trigonal bipyramids, corners with two equivalent S(9)NdEr3 trigonal pyramids, edges with two equivalent S(6)Nd2Er3 square pyramids,  an edgeedge with one S(2)Nd2Er3 trigonal bipyramid,  an edgeedge with one S(1)Nd3Er2 trigonal bipyramid, edges with two equivalent S(5)Nd2Er3 trigonal bipyramids, and  an edgeedge with one S(9)NdEr3 trigonal pyramid. In the sixth S site, S(6) is bonded to one Er(3), two equivalent Er(5), and two equivalent Nd(1) atoms to form SNd2Er3 square pyramids that share corners with two equivalent S(7)Nd2Er3 square pyramids, corners with two equivalent S(1)Nd3Er2 trigonal bipyramids, corners with two equivalent S(8)Nd3Er2 trigonal bipyramids,  an edgeedge with one S(7)Nd2Er3 square pyramid, edges with two equivalent S(6)Nd2Er3 square pyramids,  an edgeedge with one S(8)Nd3Er2 trigonal bipyramid, edges with two equivalent S(5)Nd2Er3 trigonal bipyramids, and edges with two equivalent S(9)NdEr3 trigonal pyramids. In the seventh S site, S(7) is bonded to one Er(2), two equivalent Er(6), and two equivalent Nd(1) atoms to form SNd2Er3 square pyramids that share corners with two equivalent S(6)Nd2Er3 square pyramids, corners with two equivalent S(7)Nd2Er3 square pyramids, corners with two equivalent S(8)Nd3Er2 trigonal bipyramids, corners with two equivalent S(9)NdEr3 trigonal pyramids,  an edgeedge with one S(6)Nd2Er3 square pyramid, edges with three equivalent S(7)Nd2Er3 square pyramids,  an edgeedge with one S(8)Nd3Er2 trigonal bipyramid, and edges with two equivalent S(1)Nd3Er2 trigonal bipyramids. In the eighth S site, S(8) is bonded to two equivalent Er(1), one Nd(2), and two equivalent Nd(1) atoms to form distorted SNd3Er2 trigonal bipyramids that share corners with two equivalent S(6)Nd2Er3 square pyramids, corners with two equivalent S(7)Nd2Er3 square pyramids, corners with two equivalent S(5)Nd2Er3 trigonal bipyramids, corners with four equivalent S(11)Er4 trigonal pyramids,  an edgeedge with one S(6)Nd2Er3 square pyramid,  an edgeedge with one S(7)Nd2Er3 square pyramid, edges with two equivalent S(2)Nd2Er3 trigonal bipyramids, edges with two equivalent S(1)Nd3Er2 trigonal bipyramids, edges with two equivalent S(8)Nd3Er2 trigonal bipyramids,  an edgeedge with one S(11)Er4 trigonal pyramid, and edges with two equivalent S(9)NdEr3 trigonal pyramids. In the ninth S site, S(9) is bonded to one Er(1), two equivalent Er(3), and one Nd(1) atom to form distorted SNdEr3 trigonal pyramids that share corners with two equivalent S(7)Nd2Er3 square pyramids,  a cornercorner with one S(2)Nd2Er3 trigonal bipyramid,  a cornercorner with one S(1)Nd3Er2 trigonal bipyramid, corners with two equivalent S(5)Nd2Er3 trigonal bipyramids, corners with two equivalent S(9)NdEr3 trigonal pyramids, corners with three equivalent S(11)Er4 trigonal pyramids, edges with two equivalent S(6)Nd2Er3 square pyramids,  an edgeedge with one S(5)Nd2Er3 trigonal bipyramid, and edges with two equivalent S(8)Nd3Er2 trigonal bipyramids. In the tenth S site, S(10) is bonded in a rectangular see-saw-like geometry to one Er(5), one Er(6), and two equivalent Er(2) atoms. In the eleventh S site, S(11) is bonded to one Er(4) and three equivalent Er(1) atoms to form distorted SEr4 trigonal pyramids that share  a cornercorner with one S(2)Nd2Er3 trigonal bipyramid, corners with four equivalent S(8)Nd3Er2 trigonal bipyramids, corners with two equivalent S(11)Er4 trigonal pyramids, corners with three equivalent S(9)NdEr3 trigonal pyramids,  an edgeedge with one S(8)Nd3Er2 trigonal bipyramid, edges with two equivalent S(2)Nd2Er3 trigonal bipyramids, and edges with two equivalent S(11)Er4 trigonal pyramids.