Er2ZrS5 crystallizes in the orthorhombic Pnma space group. Er(1) is bonded in a 8-coordinate geometry to two equivalent S(1), two equivalent S(2), two equivalent S(3), and two equivalent S(4) atoms. Zr(1) is bonded to one S(2), one S(3), one S(4), and four equivalent S(1) atoms to form distorted edge-sharing ZrS7 pentagonal bipyramids. There are four inequivalent S sites. In the first S site, S(1) is bonded to two equivalent Er(1) and two equivalent Zr(1) atoms to form distorted SEr2Zr2 tetrahedra that share corners with two equivalent S(4)Er4Zr square pyramids, corners with four equivalent S(3)Er4Zr square pyramids, corners with six equivalent S(1)Er2Zr2 tetrahedra, corners with two equivalent S(2)Er4Zr trigonal bipyramids,  an edgeedge with one S(3)Er4Zr square pyramid, edges with two equivalent S(4)Er4Zr square pyramids,  an edgeedge with one S(1)Er2Zr2 tetrahedra, and edges with two equivalent S(2)Er4Zr trigonal bipyramids. In the second S site, S(2) is bonded to four equivalent Er(1) and one Zr(1) atom to form distorted SEr4Zr trigonal bipyramids that share  a cornercorner with one S(4)Er4Zr square pyramid, corners with five equivalent S(3)Er4Zr square pyramids, corners with four equivalent S(1)Er2Zr2 tetrahedra, corners with four equivalent S(2)Er4Zr trigonal bipyramids, edges with two equivalent S(3)Er4Zr square pyramids, edges with four equivalent S(4)Er4Zr square pyramids, and edges with four equivalent S(1)Er2Zr2 tetrahedra. In the third S site, S(3) is bonded to four equivalent Er(1) and one Zr(1) atom to form SEr4Zr square pyramids that share corners with four equivalent S(4)Er4Zr square pyramids, corners with eight equivalent S(1)Er2Zr2 tetrahedra, corners with five equivalent S(2)Er4Zr trigonal bipyramids,  an edgeedge with one S(4)Er4Zr square pyramid, edges with two equivalent S(3)Er4Zr square pyramids, edges with two equivalent S(1)Er2Zr2 tetrahedra, edges with two equivalent S(2)Er4Zr trigonal bipyramids, and  a faceface with one S(4)Er4Zr square pyramid. In the fourth S site, S(4) is bonded to four equivalent Er(1) and one Zr(1) atom to form distorted SEr4Zr square pyramids that share corners with four equivalent S(3)Er4Zr square pyramids, corners with four equivalent S(4)Er4Zr square pyramids, corners with four equivalent S(1)Er2Zr2 tetrahedra,  a cornercorner with one S(2)Er4Zr trigonal bipyramid,  an edgeedge with one S(3)Er4Zr square pyramid, edges with four equivalent S(1)Er2Zr2 tetrahedra, edges with four equivalent S(2)Er4Zr trigonal bipyramids, and  a faceface with one S(3)Er4Zr square pyramid.
Er2ZrS5 crystallizes in the orthorhombic Pnma space group. Er(1) is bonded in a 8-coordinate geometry to two equivalent S(1), two equivalent S(2), two equivalent S(3), and two equivalent S(4) atoms. There is one shorter (2.77 Å) and one longer (2.79 Å) Er(1)-S(1) bond length. There is one shorter (2.83 Å) and one longer (2.97 Å) Er(1)-S(2) bond length. There is one shorter (2.84 Å) and one longer (2.87 Å) Er(1)-S(3) bond length. There is one shorter (2.79 Å) and one longer (2.83 Å) Er(1)-S(4) bond length. Zr(1) is bonded to one S(2), one S(3), one S(4), and four equivalent S(1) atoms to form distorted edge-sharing ZrS7 pentagonal bipyramids. The Zr(1)-S(2) bond length is 2.72 Å. The Zr(1)-S(3) bond length is 2.69 Å. The Zr(1)-S(4) bond length is 2.61 Å. There are two shorter (2.51 Å) and two longer (2.65 Å) Zr(1)-S(1) bond lengths. There are four inequivalent S sites. In the first S site, S(1) is bonded to two equivalent Er(1) and two equivalent Zr(1) atoms to form distorted SEr2Zr2 tetrahedra that share corners with two equivalent S(4)Er4Zr square pyramids, corners with four equivalent S(3)Er4Zr square pyramids, corners with six equivalent S(1)Er2Zr2 tetrahedra, corners with two equivalent S(2)Er4Zr trigonal bipyramids,  an edgeedge with one S(3)Er4Zr square pyramid, edges with two equivalent S(4)Er4Zr square pyramids,  an edgeedge with one S(1)Er2Zr2 tetrahedra, and edges with two equivalent S(2)Er4Zr trigonal bipyramids. In the second S site, S(2) is bonded to four equivalent Er(1) and one Zr(1) atom to form distorted SEr4Zr trigonal bipyramids that share  a cornercorner with one S(4)Er4Zr square pyramid, corners with five equivalent S(3)Er4Zr square pyramids, corners with four equivalent S(1)Er2Zr2 tetrahedra, corners with four equivalent S(2)Er4Zr trigonal bipyramids, edges with two equivalent S(3)Er4Zr square pyramids, edges with four equivalent S(4)Er4Zr square pyramids, and edges with four equivalent S(1)Er2Zr2 tetrahedra. In the third S site, S(3) is bonded to four equivalent Er(1) and one Zr(1) atom to form SEr4Zr square pyramids that share corners with four equivalent S(4)Er4Zr square pyramids, corners with eight equivalent S(1)Er2Zr2 tetrahedra, corners with five equivalent S(2)Er4Zr trigonal bipyramids,  an edgeedge with one S(4)Er4Zr square pyramid, edges with two equivalent S(3)Er4Zr square pyramids, edges with two equivalent S(1)Er2Zr2 tetrahedra, edges with two equivalent S(2)Er4Zr trigonal bipyramids, and  a faceface with one S(4)Er4Zr square pyramid. In the fourth S site, S(4) is bonded to four equivalent Er(1) and one Zr(1) atom to form distorted SEr4Zr square pyramids that share corners with four equivalent S(3)Er4Zr square pyramids, corners with four equivalent S(4)Er4Zr square pyramids, corners with four equivalent S(1)Er2Zr2 tetrahedra,  a cornercorner with one S(2)Er4Zr trigonal bipyramid,  an edgeedge with one S(3)Er4Zr square pyramid, edges with four equivalent S(1)Er2Zr2 tetrahedra, edges with four equivalent S(2)Er4Zr trigonal bipyramids, and  a faceface with one S(3)Er4Zr square pyramid.