Pr(ErS2)3 crystallizes in the monoclinic P2_1/m space group. There are three inequivalent Er sites. In the first Er site, Er(1) is bonded to one S(2), one S(5), two equivalent S(6), and three equivalent S(1) atoms to form distorted ErS7 pentagonal bipyramids that share  a cornercorner with one Er(2)S6 octahedra, corners with two equivalent Er(3)S6 octahedra, edges with two equivalent Er(2)S6 octahedra, and edges with four equivalent Er(1)S7 pentagonal bipyramids. The corner-sharing octahedral tilt angles range from 39-51°. In the second Er site, Er(2) is bonded to one S(1), two equivalent S(5), 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(2)S6 octahedra, and edges with two equivalent Er(1)S7 pentagonal bipyramids. The corner-sharing octahedral tilt angles range from 54-62°. In the third Er site, Er(3) is bonded to one S(3), two equivalent S(2), and three equivalent S(4) atoms to form ErS6 octahedra that share corners with three equivalent Er(2)S6 octahedra, corners with two equivalent Er(1)S7 pentagonal bipyramids, and edges with four equivalent Er(3)S6 octahedra. The corner-sharing octahedral tilt angles range from 54-62°. Pr(1) is bonded in a 8-coordinate geometry to one S(2), two equivalent S(4), two equivalent S(5), and three equivalent S(6) atoms. There are six inequivalent S sites. In the first S site, S(1) is bonded to one Er(2) and three equivalent Er(1) atoms to form distorted SEr4 trigonal pyramids that share  a cornercorner with one S(5)Pr2Er3 trigonal bipyramid, corners with four equivalent S(6)Pr3Er2 trigonal bipyramids, corners with two equivalent S(1)Er4 trigonal pyramids, corners with three equivalent S(2)PrEr3 trigonal pyramids,  an edgeedge with one S(6)Pr3Er2 trigonal bipyramid, edges with two equivalent S(5)Pr2Er3 trigonal bipyramids, and edges with two equivalent S(1)Er4 trigonal pyramids. In the second S site, S(2) is bonded to one Er(1), two equivalent Er(3), and one Pr(1) atom to form distorted SPrEr3 trigonal pyramids that share corners with two equivalent S(4)Pr2Er3 square pyramids,  a cornercorner with one S(6)Pr3Er2 trigonal bipyramid, corners with three equivalent S(5)Pr2Er3 trigonal bipyramids, corners with two equivalent S(2)PrEr3 trigonal pyramids, corners with three equivalent S(1)Er4 trigonal pyramids, edges with three equivalent S(4)Pr2Er3 square pyramids, and edges with two equivalent S(6)Pr3Er2 trigonal bipyramids. In the third S site, S(3) is bonded in a rectangular see-saw-like geometry to one Er(3) and three equivalent Er(2) atoms. In the fourth S site, S(4) is bonded to three equivalent Er(3) and two equivalent Pr(1) atoms to form SPr2Er3 square pyramids that share corners with two equivalent S(5)Pr2Er3 trigonal bipyramids, corners with four equivalent S(6)Pr3Er2 trigonal bipyramids, corners with two equivalent S(2)PrEr3 trigonal pyramids, edges with four equivalent S(4)Pr2Er3 square pyramids,  an edgeedge with one S(5)Pr2Er3 trigonal bipyramid,  an edgeedge with one S(6)Pr3Er2 trigonal bipyramid, and edges with three equivalent S(2)PrEr3 trigonal pyramids. In the fifth S site, S(5) is bonded to one Er(1), two equivalent Er(2), and two equivalent Pr(1) atoms to form distorted SPr2Er3 trigonal bipyramids that share corners with two equivalent S(4)Pr2Er3 square pyramids, corners with two equivalent S(6)Pr3Er2 trigonal bipyramids,  a cornercorner with one S(1)Er4 trigonal pyramid, corners with three equivalent S(2)PrEr3 trigonal pyramids,  an edgeedge with one S(4)Pr2Er3 square pyramid, edges with two equivalent S(5)Pr2Er3 trigonal bipyramids, edges with three equivalent S(6)Pr3Er2 trigonal bipyramids, and edges with two equivalent S(1)Er4 trigonal pyramids. In the sixth S site, S(6) is bonded to two equivalent Er(1) and three equivalent Pr(1) atoms to form distorted SPr3Er2 trigonal bipyramids that share corners with four equivalent S(4)Pr2Er3 square pyramids, corners with two equivalent S(5)Pr2Er3 trigonal bipyramids,  a cornercorner with one S(2)PrEr3 trigonal pyramid, corners with four equivalent S(1)Er4 trigonal pyramids,  an edgeedge with one S(4)Pr2Er3 square pyramid, edges with three equivalent S(5)Pr2Er3 trigonal bipyramids, edges with four equivalent S(6)Pr3Er2 trigonal bipyramids,  an edgeedge with one S(1)Er4 trigonal pyramid, and edges with two equivalent S(2)PrEr3 trigonal pyramids.
Pr(ErS2)3 crystallizes in the monoclinic P2_1/m space group. There are three inequivalent Er sites. In the first Er site, Er(1) is bonded to one S(2), one S(5), two equivalent S(6), and three equivalent S(1) atoms to form distorted ErS7 pentagonal bipyramids that share  a cornercorner with one Er(2)S6 octahedra, corners with two equivalent Er(3)S6 octahedra, edges with two equivalent Er(2)S6 octahedra, and edges with four equivalent Er(1)S7 pentagonal bipyramids. The corner-sharing octahedral tilt angles range from 39-51°. The Er(1)-S(2) bond length is 2.70 Å. The Er(1)-S(5) bond length is 2.84 Å. Both Er(1)-S(6) bond lengths are 2.90 Å. There are two shorter (2.67 Å) and one longer (2.87 Å) Er(1)-S(1) bond length. In the second Er site, Er(2) is bonded to one S(1), two equivalent S(5), 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(2)S6 octahedra, and edges with two equivalent Er(1)S7 pentagonal bipyramids. The corner-sharing octahedral tilt angles range from 54-62°. The Er(2)-S(1) bond length is 2.65 Å. Both Er(2)-S(5) bond lengths are 2.75 Å. There are two shorter (2.69 Å) and one longer (2.75 Å) Er(2)-S(3) bond length. In the third Er site, Er(3) is bonded to one S(3), two equivalent S(2), and three equivalent S(4) atoms to form ErS6 octahedra that share corners with three equivalent Er(2)S6 octahedra, corners with two equivalent Er(1)S7 pentagonal bipyramids, and edges with four equivalent Er(3)S6 octahedra. The corner-sharing octahedral tilt angles range from 54-62°. The Er(3)-S(3) bond length is 2.68 Å. Both Er(3)-S(2) bond lengths are 2.63 Å. There is one shorter (2.70 Å) and two longer (2.77 Å) Er(3)-S(4) bond lengths. Pr(1) is bonded in a 8-coordinate geometry to one S(2), two equivalent S(4), two equivalent S(5), and three equivalent S(6) atoms. The Pr(1)-S(2) bond length is 3.00 Å. Both Pr(1)-S(4) bond lengths are 3.04 Å. Both Pr(1)-S(5) bond lengths are 3.04 Å. There are two shorter (2.91 Å) and one longer (2.96 Å) Pr(1)-S(6) bond length. There are six inequivalent S sites. In the first S site, S(1) is bonded to one Er(2) and three equivalent Er(1) atoms to form distorted SEr4 trigonal pyramids that share  a cornercorner with one S(5)Pr2Er3 trigonal bipyramid, corners with four equivalent S(6)Pr3Er2 trigonal bipyramids, corners with two equivalent S(1)Er4 trigonal pyramids, corners with three equivalent S(2)PrEr3 trigonal pyramids,  an edgeedge with one S(6)Pr3Er2 trigonal bipyramid, edges with two equivalent S(5)Pr2Er3 trigonal bipyramids, and edges with two equivalent S(1)Er4 trigonal pyramids. In the second S site, S(2) is bonded to one Er(1), two equivalent Er(3), and one Pr(1) atom to form distorted SPrEr3 trigonal pyramids that share corners with two equivalent S(4)Pr2Er3 square pyramids,  a cornercorner with one S(6)Pr3Er2 trigonal bipyramid, corners with three equivalent S(5)Pr2Er3 trigonal bipyramids, corners with two equivalent S(2)PrEr3 trigonal pyramids, corners with three equivalent S(1)Er4 trigonal pyramids, edges with three equivalent S(4)Pr2Er3 square pyramids, and edges with two equivalent S(6)Pr3Er2 trigonal bipyramids. In the third S site, S(3) is bonded in a rectangular see-saw-like geometry to one Er(3) and three equivalent Er(2) atoms. In the fourth S site, S(4) is bonded to three equivalent Er(3) and two equivalent Pr(1) atoms to form SPr2Er3 square pyramids that share corners with two equivalent S(5)Pr2Er3 trigonal bipyramids, corners with four equivalent S(6)Pr3Er2 trigonal bipyramids, corners with two equivalent S(2)PrEr3 trigonal pyramids, edges with four equivalent S(4)Pr2Er3 square pyramids,  an edgeedge with one S(5)Pr2Er3 trigonal bipyramid,  an edgeedge with one S(6)Pr3Er2 trigonal bipyramid, and edges with three equivalent S(2)PrEr3 trigonal pyramids. In the fifth S site, S(5) is bonded to one Er(1), two equivalent Er(2), and two equivalent Pr(1) atoms to form distorted SPr2Er3 trigonal bipyramids that share corners with two equivalent S(4)Pr2Er3 square pyramids, corners with two equivalent S(6)Pr3Er2 trigonal bipyramids,  a cornercorner with one S(1)Er4 trigonal pyramid, corners with three equivalent S(2)PrEr3 trigonal pyramids,  an edgeedge with one S(4)Pr2Er3 square pyramid, edges with two equivalent S(5)Pr2Er3 trigonal bipyramids, edges with three equivalent S(6)Pr3Er2 trigonal bipyramids, and edges with two equivalent S(1)Er4 trigonal pyramids. In the sixth S site, S(6) is bonded to two equivalent Er(1) and three equivalent Pr(1) atoms to form distorted SPr3Er2 trigonal bipyramids that share corners with four equivalent S(4)Pr2Er3 square pyramids, corners with two equivalent S(5)Pr2Er3 trigonal bipyramids,  a cornercorner with one S(2)PrEr3 trigonal pyramid, corners with four equivalent S(1)Er4 trigonal pyramids,  an edgeedge with one S(4)Pr2Er3 square pyramid, edges with three equivalent S(5)Pr2Er3 trigonal bipyramids, edges with four equivalent S(6)Pr3Er2 trigonal bipyramids,  an edgeedge with one S(1)Er4 trigonal pyramid, and edges with two equivalent S(2)PrEr3 trigonal pyramids.