Er2O2S crystallizes in the trigonal P-3m1 space group. Er(1) is bonded in a 7-coordinate geometry to three equivalent S(1) and four equivalent O(1) atoms. S(1) is bonded to six equivalent Er(1) atoms to form SEr6 octahedra that share corners with twelve equivalent O(1)Er4 tetrahedra, edges with six equivalent S(1)Er6 octahedra, and edges with six equivalent O(1)Er4 tetrahedra. O(1) is bonded to four equivalent Er(1) atoms to form OEr4 tetrahedra that share corners with six equivalent S(1)Er6 octahedra, corners with six equivalent O(1)Er4 tetrahedra, edges with three equivalent S(1)Er6 octahedra, and edges with three equivalent O(1)Er4 tetrahedra. The corner-sharing octahedral tilt angles range from 26-49°.
Er2O2S crystallizes in the trigonal P-3m1 space group. Er(1) is bonded in a 7-coordinate geometry to three equivalent S(1) and four equivalent O(1) atoms. All Er(1)-S(1) bond lengths are 2.84 Å. There are three shorter (2.23 Å) and one longer (2.25 Å) Er(1)-O(1) bond length. S(1) is bonded to six equivalent Er(1) atoms to form SEr6 octahedra that share corners with twelve equivalent O(1)Er4 tetrahedra, edges with six equivalent S(1)Er6 octahedra, and edges with six equivalent O(1)Er4 tetrahedra. O(1) is bonded to four equivalent Er(1) atoms to form OEr4 tetrahedra that share corners with six equivalent S(1)Er6 octahedra, corners with six equivalent O(1)Er4 tetrahedra, edges with three equivalent S(1)Er6 octahedra, and edges with three equivalent O(1)Er4 tetrahedra. The corner-sharing octahedral tilt angles range from 26-49°.