DOE OSTI2020
Er2S3 crystallizes in the monoclinic P2_1/m space group. The structure is three-dimensional. there are six inequivalent Er3+ sites. In the first Er3+ site, Er3+ is bonded to seven S2- atoms to form distorted ErS7 pentagonal bipyramids that share corners with five ErS6 octahedra, edges with four ErS6 octahedra, edges with four equivalent ErS7 pentagonal bipyramids, and a faceface with one ErS6 octahedra. The corner-sharing octahedra tilt angles range from 32–49°. There are a spread of Er–S bond distances ranging from 2.67–2.91 Å. In the second Er3+ site, Er3+ is bonded to seven S2- atoms to form distorted ErS7 pentagonal bipyramids that share corners with three ErS6 octahedra, corners with two equivalent ErS7 pentagonal bipyramids, edges with two equivalent ErS6 octahedra, edges with six ErS7 pentagonal bipyramids, and a faceface with one ErS7 pentagonal bipyramid. The corner-sharing octahedra tilt angles range from 49–51°. There are a spread of Er–S bond distances ranging from 2.70–2.94 Å. In the third Er3+ site, Er3+ is bonded to seven S2- atoms to form distorted ErS7 pentagonal bipyramids that share corners with two ErS6 octahedra, corners with two equivalent ErS7 pentagonal bipyramids, edges with two equivalent ErS6 octahedra, edges with six ErS7 pentagonal bipyramids, and a faceface with one ErS7 pentagonal bipyramid. The corner-sharing octahedra tilt angles range from 33–34°. There are a spread of Er–S bond distances ranging from 2.71–2.93 Å. In the fourth Er3+ site, Er3+ is bonded to six S2- atoms to form ErS6 octahedra that share corners with four ErS6 octahedra, corners with five ErS7 pentagonal bipyramids, edges with four equivalent ErS6 octahedra, and a faceface with one ErS7 pentagonal bipyramid. The corner-sharing octahedra tilt angles range from 63–67°. There are a spread of Er–S bond distances ranging from 2.67–2.82 Å. In the fifth Er3+ site, Er3+ is bonded to six S2- atoms to form ErS6 octahedra that share corners with four ErS6 octahedra, corners with three ErS7 pentagonal bipyramids, edges with three ErS6 octahedra, and edges with four ErS7 pentagonal bipyramids. The corner-sharing octahedra tilt angles range from 14–67°. There are a spread of Er–S bond distances ranging from 2.62–2.81 Å. In the sixth Er3+ site, Er3+ is bonded to six S2- atoms to form ErS6 octahedra that share corners with four ErS6 octahedra, corners with two ErS7 pentagonal bipyramids, edges with three ErS6 octahedra, and edges with four ErS7 pentagonal bipyramids. The corner-sharing octahedra tilt angles range from 14–63°. There are a spread of Er–S bond distances ranging from 2.67–2.84 Å. There are nine inequivalent S2- sites. In the first S2- site, S2- is bonded to five Er3+ atoms to form distorted SEr5 trigonal bipyramids that share corners with seven SEr4 trigonal pyramids, edges with four equivalent SEr5 trigonal bipyramids, and edges with six SEr4 trigonal pyramids. In the second S2- site, S2- is bonded to five Er3+ atoms to form distorted SEr5 trigonal bipyramids that share corners with four equivalent SEr4 tetrahedra, corners with five SEr4 trigonal pyramids, edges with two equivalent SEr5 square pyramids, an edgeedge with one SEr4 tetrahedra, edges with two equivalent SEr5 trigonal bipyramids, and edges with three equivalent SEr4 trigonal pyramids. In the third S2- site, S2- is bonded to five Er3+ atoms to form SEr5 square pyramids that share a cornercorner with one SEr4 tetrahedra, corners with seven SEr4 trigonal pyramids, edges with two equivalent SEr5 square pyramids, edges with two equivalent SEr4 tetrahedra, edges with two equivalent SEr5 trigonal bipyramids, and an edgeedge with one SEr4 trigonal pyramid. In the fourth S2- site, S2- is bonded to four Er3+ atoms to form SEr4 trigonal pyramids that share a cornercorner with one SEr5 square pyramid, corners with three equivalent SEr4 tetrahedra, corners with two equivalent SEr5 trigonal bipyramids, corners with two equivalent SEr4 trigonal pyramids, edges with three equivalent SEr5 trigonal bipyramids, and edges with two equivalent SEr4 trigonal pyramids. In the fifth S2- site, S2- is bonded in a distorted rectangular see-saw-like geometry to four Er3+ atoms. In the sixth S2- site, S2- is bonded to four Er3+ atoms to form distorted SEr4 trigonal pyramids that share corners with two equivalent SEr5 square pyramids, a cornercorner with one SEr4 tetrahedra, corners with two equivalent SEr5 trigonal bipyramids, corners with eight SEr4 trigonal pyramids, and edges with three equivalent SEr5 trigonal bipyramids. In the seventh S2- site, S2- is bonded to four Er3+ atoms to form distorted SEr4 trigonal pyramids that share corners with two equivalent SEr5 square pyramids, corners with five SEr5 trigonal bipyramids, corners with six SEr4 trigonal pyramids, an edgeedge with one SEr5 trigonal bipyramid, and edges with four SEr4 trigonal pyramids. In the eighth S2- site, S2- is bonded to four Er3+ atoms to form distorted SEr4 tetrahedra that share a cornercorner with one SEr5 square pyramid, corners with two equivalent SEr4 tetrahedra, corners with four equivalent SEr5 trigonal bipyramids, corners with four SEr4 trigonal pyramids, edges with two equivalent SEr5 square pyramids, edges with two equivalent SEr4 tetrahedra, and an edgeedge with one SEr5 trigonal bipyramid. In the ninth S2- site, S2- is bonded to four Er3+ atoms to form distorted SEr4 trigonal pyramids that share corners with two equivalent SEr5 square pyramids, corners with three SEr5 trigonal bipyramids, corners with six SEr4 trigonal pyramids, an edgeedge with one SEr5 square pyramid, edges with two equivalent SEr5 trigonal bipyramids, and edges with two equivalent SEr4 trigonal pyramids.