DOE OSTI2020
Er3SmS6 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 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 56–61°. There are a spread of Er–S bond distances ranging from 2.64–2.77 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, 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 2.67–2.91 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, 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 56–61°. There are a spread of Er–S bond distances ranging from 2.65–2.76 Å. Sm3+ is bonded in a 8-coordinate geometry to eight S2- atoms. There are a spread of Sm–S bond distances ranging from 2.86–3.02 Å. There are six inequivalent S2- sites. In the first S2- site, S2- is bonded to three Er3+ and one Sm3+ atom to form distorted SSmEr3 trigonal pyramids that share corners with two equivalent SSm2Er3 square pyramids, corners with four SSm3Er2 trigonal bipyramids, corners with two equivalent SSmEr3 trigonal pyramids, edges with three equivalent SSm2Er3 square pyramids, and edges with two equivalent SSm3Er2 trigonal bipyramids. In the second S2- site, S2- is bonded to three equivalent Er3+ and two equivalent Sm3+ atoms to form distorted SSm2Er3 square pyramids that share corners with six SSm2Er3 trigonal bipyramids, corners with two equivalent SSmEr3 trigonal pyramids, edges with four equivalent SSm2Er3 square pyramids, edges with two SSm2Er3 trigonal bipyramids, and edges with three equivalent SSmEr3 trigonal pyramids. In the third S2- site, S2- is bonded to two equivalent Er3+ and three equivalent Sm3+ atoms to form distorted SSm3Er2 trigonal bipyramids that share corners with four equivalent SSm2Er3 square pyramids, corners with two equivalent SSm2Er3 trigonal bipyramids, a cornercorner with one SSmEr3 trigonal pyramid, an edgeedge with one SSm2Er3 square pyramid, edges with seven SSm3Er2 trigonal bipyramids, and edges with two equivalent SSmEr3 trigonal pyramids. In the fourth S2- site, S2- is bonded in a 4-coordinate geometry to four Er3+ atoms. In the fifth S2- site, S2- is bonded in a rectangular see-saw-like geometry to four Er3+ atoms. In the sixth S2- site, S2- is bonded to three Er3+ and two equivalent Sm3+ atoms to form distorted SSm2Er3 trigonal bipyramids that share corners with two equivalent SSm2Er3 square pyramids, corners with two equivalent SSm3Er2 trigonal bipyramids, corners with three equivalent SSmEr3 trigonal pyramids, an edgeedge with one SSm2Er3 square pyramid, and edges with five SSm3Er2 trigonal bipyramids.