DOE OSTI2020
Rb3Er7S12 crystallizes in the orthorhombic Pmn2_1 space group. The structure is three-dimensional. there are three inequivalent Rb1+ sites. In the first Rb1+ site, Rb1+ is bonded in a 7-coordinate geometry to seven S2- atoms. There are a spread of Rb–S bond distances ranging from 3.44–3.56 Å. In the second Rb1+ site, Rb1+ is bonded in a 7-coordinate geometry to seven S2- atoms. There are a spread of Rb–S bond distances ranging from 3.35–3.57 Å. In the third Rb1+ site, Rb1+ is bonded in a 6-coordinate geometry to six S2- atoms. There are a spread of Rb–S bond distances ranging from 3.26–3.73 Å. There are seven inequivalent Er3+ sites. In the first Er3+ site, Er3+ is bonded to six S2- atoms to form a mixture of corner and edge-sharing ErS6 octahedra. The corner-sharing octahedra tilt angles range from 3–14°. There are a spread of Er–S bond distances ranging from 2.67–2.85 Å. In the second Er3+ site, Er3+ is bonded to six S2- atoms to form a mixture of corner and edge-sharing ErS6 octahedra. The corner-sharing octahedra tilt angles range from 2–14°. There are a spread of Er–S bond distances ranging from 2.66–2.84 Å. In the third Er3+ site, Er3+ is bonded to six S2- atoms to form a mixture of corner and edge-sharing ErS6 octahedra. The corner-sharing octahedral tilt angles are 3°. There are a spread of Er–S bond distances ranging from 2.66–2.86 Å. In the fourth Er3+ site, Er3+ is bonded to six S2- atoms to form a mixture of corner and edge-sharing ErS6 octahedra. The corner-sharing octahedral tilt angles are 2°. There are a spread of Er–S bond distances ranging from 2.68–2.90 Å. In the fifth Er3+ site, Er3+ is bonded to six S2- atoms to form edge-sharing ErS6 octahedra. There are a spread of Er–S bond distances ranging from 2.66–2.87 Å. In the sixth Er3+ site, Er3+ is bonded to six S2- atoms to form edge-sharing ErS6 octahedra. There are a spread of Er–S bond distances ranging from 2.69–2.83 Å. In the seventh Er3+ site, Er3+ is bonded to six S2- atoms to form a mixture of corner and edge-sharing ErS6 octahedra. The corner-sharing octahedral tilt angles are 14°. There are a spread of Er–S bond distances ranging from 2.72–2.78 Å. There are twelve inequivalent S2- sites. In the first S2- site, S2- is bonded to two equivalent Rb1+ and three Er3+ atoms to form distorted SRb2Er3 square pyramids that share corners with two equivalent SRbEr4 trigonal bipyramids, edges with four SRb2Er3 square pyramids, and an edgeedge with one SRbEr4 trigonal bipyramid. In the second S2- site, S2- is bonded in a 5-coordinate geometry to two equivalent Rb1+ and three Er3+ atoms. In the third S2- site, S2- is bonded to five Er3+ atoms to form SEr5 square pyramids that share corners with two equivalent SRb2Er3 trigonal bipyramids, edges with four SRb2Er3 square pyramids, and edges with two equivalent SRbEr4 trigonal bipyramids. In the fourth S2- site, S2- is bonded to five Er3+ atoms to form SEr5 square pyramids that share corners with two equivalent SRb2Er3 trigonal bipyramids, edges with two equivalent SEr5 square pyramids, and an edgeedge with one SRb2Er3 trigonal bipyramid. In the fifth S2- site, S2- is bonded in a 5-coordinate geometry to two equivalent Rb1+ and three Er3+ atoms. In the sixth S2- site, S2- is bonded in a 6-coordinate geometry to three Rb1+ and three Er3+ atoms. In the seventh S2- site, S2- is bonded in a 5-coordinate geometry to two equivalent Rb1+ and three Er3+ atoms. In the eighth S2- site, S2- is bonded in a 5-coordinate geometry to two equivalent Rb1+ and three Er3+ atoms. In the ninth S2- site, S2- is bonded to two equivalent Rb1+ and three Er3+ atoms to form distorted SRb2Er3 trigonal bipyramids that share corners with four SEr5 square pyramids, a cornercorner with one SRbEr4 trigonal bipyramid, an edgeedge with one SEr5 square pyramid, and edges with two equivalent SRb2Er3 trigonal bipyramids. In the tenth S2- site, S2- is bonded in a 6-coordinate geometry to three Rb1+ and three Er3+ atoms. In the eleventh S2- site, S2- is bonded to one Rb1+ and four Er3+ atoms to form a mixture of distorted corner and edge-sharing SRbEr4 trigonal bipyramids. In the twelfth S2- site, S2- is bonded in a 5-coordinate geometry to one Rb1+ and four Er3+ atoms.