Er3S3OF crystallizes in the tetragonal I-4m2 space group. There are two inequivalent Er sites. In the first Er site, Er(1) is bonded to two equivalent S(2) and four equivalent S(1) atoms to form a mixture of edge and corner-sharing ErS6 octahedra. The corner-sharing octahedra are not tilted. In the second Er site, Er(2) is bonded in a 8-coordinate geometry to four equivalent S(2), two equivalent O(1), and two equivalent F(1) atoms. There are two inequivalent S sites. In the first S site, S(1) is bonded in a square co-planar geometry to four equivalent Er(1) atoms. In the second S site, S(2) is bonded in a 5-coordinate geometry to one Er(1) and four equivalent Er(2) atoms. O(1) is bonded to four equivalent Er(2) atoms to form OEr4 tetrahedra that share corners with four equivalent O(1)Er4 tetrahedra and edges with four equivalent F(1)Er4 tetrahedra. F(1) is bonded to four equivalent Er(2) atoms to form FEr4 tetrahedra that share corners with four equivalent F(1)Er4 tetrahedra and edges with four equivalent O(1)Er4 tetrahedra.
Er3S3OF crystallizes in the tetragonal I-4m2 space group. There are two inequivalent Er sites. In the first Er site, Er(1) is bonded to two equivalent S(2) and four equivalent S(1) atoms to form a mixture of edge and corner-sharing ErS6 octahedra. The corner-sharing octahedra are not tilted. Both Er(1)-S(2) bond lengths are 2.70 Å. All Er(1)-S(1) bond lengths are 2.66 Å. In the second Er site, Er(2) is bonded in a 8-coordinate geometry to four equivalent S(2), two equivalent O(1), and two equivalent F(1) atoms. All Er(2)-S(2) bond lengths are 2.92 Å. Both Er(2)-O(1) bond lengths are 2.31 Å. Both Er(2)-F(1) bond lengths are 2.31 Å. There are two inequivalent S sites. In the first S site, S(1) is bonded in a square co-planar geometry to four equivalent Er(1) atoms. In the second S site, S(2) is bonded in a 5-coordinate geometry to one Er(1) and four equivalent Er(2) atoms. O(1) is bonded to four equivalent Er(2) atoms to form OEr4 tetrahedra that share corners with four equivalent O(1)Er4 tetrahedra and edges with four equivalent F(1)Er4 tetrahedra. F(1) is bonded to four equivalent Er(2) atoms to form FEr4 tetrahedra that share corners with four equivalent F(1)Er4 tetrahedra and edges with four equivalent O(1)Er4 tetrahedra.