DOE OSTI2020
La(ErS2)3 crystallizes in the monoclinic P2_1/m space group. The structure is three-dimensional. there are three 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 three ErS6 octahedra, edges with two equivalent ErS6 octahedra, and edges with four equivalent ErS7 pentagonal bipyramids. The corner-sharing octahedra tilt angles range from 38–51°. There are a spread of Er–S bond distances ranging from 2.69–2.91 Å. In the second Er3+ site, Er3+ is bonded to six S2- atoms to form ErS6 octahedra that share corners with three equivalent ErS6 octahedra, a cornercorner with one ErS7 pentagonal bipyramid, edges with four equivalent ErS6 octahedra, and edges with two equivalent ErS7 pentagonal bipyramids. The corner-sharing octahedra tilt angles range from 54–62°. There are a spread of Er–S bond distances ranging from 2.67–2.77 Å. In the third Er3+ site, Er3+ is bonded to six S2- atoms to form ErS6 octahedra that share corners with three equivalent ErS6 octahedra, corners with two equivalent ErS7 pentagonal bipyramids, and edges with four equivalent ErS6 octahedra. The corner-sharing octahedra tilt angles range from 54–62°. There are a spread of Er–S bond distances ranging from 2.65–2.79 Å. La3+ is bonded in a 8-coordinate geometry to eight S2- atoms. There are a spread of La–S bond distances ranging from 2.94–3.07 Å. There are six inequivalent S2- sites. In the first S2- site, S2- is bonded in a distorted rectangular see-saw-like geometry to four Er3+ atoms. In the second S2- site, S2- is bonded to three Er3+ and one La3+ atom to form distorted SLaEr3 trigonal pyramids that share corners with two equivalent SLa2Er3 square pyramids, corners with four SLa3Er2 trigonal bipyramids, corners with two equivalent SLaEr3 trigonal pyramids, edges with three equivalent SLa2Er3 square pyramids, and edges with two equivalent SLa3Er2 trigonal bipyramids. In the third S2- site, S2- is bonded in a 4-coordinate geometry to four Er3+ atoms. In the fourth S2- site, S2- is bonded to two equivalent Er3+ and three equivalent La3+ atoms to form distorted SLa3Er2 trigonal bipyramids that share corners with four equivalent SLa2Er3 square pyramids, corners with two equivalent SLa2Er3 trigonal bipyramids, a cornercorner with one SLaEr3 trigonal pyramid, an edgeedge with one SLa2Er3 square pyramid, edges with seven SLa3Er2 trigonal bipyramids, and edges with two equivalent SLaEr3 trigonal pyramids. In the fifth S2- site, S2- is bonded to three Er3+ and two equivalent La3+ atoms to form distorted SLa2Er3 trigonal bipyramids that share corners with two equivalent SLa2Er3 square pyramids, corners with two equivalent SLa3Er2 trigonal bipyramids, corners with three equivalent SLaEr3 trigonal pyramids, an edgeedge with one SLa2Er3 square pyramid, and edges with five SLa3Er2 trigonal bipyramids. In the sixth S2- site, S2- is bonded to three equivalent Er3+ and two equivalent La3+ atoms to form distorted SLa2Er3 square pyramids that share corners with six SLa2Er3 trigonal bipyramids, corners with two equivalent SLaEr3 trigonal pyramids, edges with four equivalent SLa2Er3 square pyramids, edges with two SLa2Er3 trigonal bipyramids, and edges with three equivalent SLaEr3 trigonal pyramids.