ErAsS is Matlockite structured and crystallizes in the orthorhombic Pmmn space group. Er(1) is bonded in a 9-coordinate geometry to four equivalent As(1) and five equivalent S(1) atoms. As(1) is bonded to four equivalent Er(1) and four equivalent As(1) atoms to form distorted AsEr4As4 hexagonal bipyramids that share corners with four equivalent As(1)Er4As4 hexagonal bipyramids, corners with twelve equivalent S(1)Er5 trigonal bipyramids, edges with four equivalent As(1)Er4As4 hexagonal bipyramids, edges with four equivalent S(1)Er5 trigonal bipyramids, and faces with four equivalent As(1)Er4As4 hexagonal bipyramids. S(1) is bonded to five equivalent Er(1) atoms to form distorted SEr5 trigonal bipyramids that share corners with twelve equivalent As(1)Er4As4 hexagonal bipyramids, corners with four equivalent S(1)Er5 trigonal bipyramids, edges with four equivalent As(1)Er4As4 hexagonal bipyramids, and edges with eight equivalent S(1)Er5 trigonal bipyramids.
ErAsS is Matlockite structured and crystallizes in the orthorhombic Pmmn space group. Er(1) is bonded in a 9-coordinate geometry to four equivalent As(1) and five equivalent S(1) atoms. There are two shorter (3.10 Å) and two longer (3.14 Å) Er(1)-As(1) bond lengths. There are four shorter (2.79 Å) and one longer (2.83 Å) Er(1)-S(1) bond length. As(1) is bonded to four equivalent Er(1) and four equivalent As(1) atoms to form distorted AsEr4As4 hexagonal bipyramids that share corners with four equivalent As(1)Er4As4 hexagonal bipyramids, corners with twelve equivalent S(1)Er5 trigonal bipyramids, edges with four equivalent As(1)Er4As4 hexagonal bipyramids, edges with four equivalent S(1)Er5 trigonal bipyramids, and faces with four equivalent As(1)Er4As4 hexagonal bipyramids. All As(1)-As(1) bond lengths are 2.70 Å. S(1) is bonded to five equivalent Er(1) atoms to form distorted SEr5 trigonal bipyramids that share corners with twelve equivalent As(1)Er4As4 hexagonal bipyramids, corners with four equivalent S(1)Er5 trigonal bipyramids, edges with four equivalent As(1)Er4As4 hexagonal bipyramids, and edges with eight equivalent S(1)Er5 trigonal bipyramids.