ErAsSe crystallizes in the orthorhombic Pnma space group. Er(1) is bonded in a 9-coordinate geometry to four equivalent As(1) and five equivalent Se(1) atoms. As(1) is bonded in a 8-coordinate geometry to four equivalent Er(1) and four equivalent As(1) atoms. Se(1) is bonded to five equivalent Er(1) atoms to form a mixture of distorted corner and edge-sharing SeEr5 trigonal bipyramids.
ErAsSe crystallizes in the orthorhombic Pnma space group. Er(1) is bonded in a 9-coordinate geometry to four equivalent As(1) and five equivalent Se(1) atoms. There are a spread of Er(1)-As(1) bond distances ranging from 3.03-3.15 Å. There are a spread of Er(1)-Se(1) bond distances ranging from 2.86-2.99 Å. As(1) is bonded in a 8-coordinate geometry to four equivalent Er(1) and four equivalent As(1) atoms. There are two shorter (2.55 Å) and two longer (2.96 Å) As(1)-As(1) bond lengths. Se(1) is bonded to five equivalent Er(1) atoms to form a mixture of distorted corner and edge-sharing SeEr5 trigonal bipyramids.