DOE OSTI2020
Rb2Sb4S7 crystallizes in the triclinic P-1 space group. The structure is three-dimensional. there are two inequivalent Rb1+ sites. In the first Rb1+ site, Rb1+ is bonded to six S2- atoms to form distorted RbS6 octahedra that share corners with two equivalent SbS5 square pyramids, an edgeedge with one RbS6 octahedra, and edges with two equivalent SbS5 square pyramids. There are a spread of Rb–S bond distances ranging from 3.34–3.40 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 3.32–3.88 Å. There are four inequivalent Sb3+ sites. In the first Sb3+ site, Sb3+ is bonded in a see-saw-like geometry to four S2- atoms. There are a spread of Sb–S bond distances ranging from 2.44–2.77 Å. In the second Sb3+ site, Sb3+ is bonded in a distorted see-saw-like geometry to four S2- atoms. There are a spread of Sb–S bond distances ranging from 2.48–3.17 Å. In the third Sb3+ site, Sb3+ is bonded to five S2- atoms to form distorted SbS5 square pyramids that share corners with two equivalent RbS6 octahedra, edges with two equivalent RbS6 octahedra, and an edgeedge with one SbS5 square pyramid. The corner-sharing octahedra tilt angles range from 27–92°. There are a spread of Sb–S bond distances ranging from 2.45–3.26 Å. In the fourth Sb3+ site, Sb3+ is bonded in a distorted rectangular see-saw-like geometry to four S2- atoms. There are a spread of Sb–S bond distances ranging from 2.46–2.95 Å. There are seven inequivalent S2- sites. In the first S2- site, S2- is bonded in a 5-coordinate geometry to one Rb1+ and four Sb3+ atoms. In the second S2- site, S2- is bonded to two equivalent Rb1+ and two Sb3+ atoms to form distorted SRb2Sb2 trigonal pyramids that share a cornercorner with one SRb2Sb3 square pyramid, corners with three equivalent SRb2Sb2 tetrahedra, a cornercorner with one SRb3Sb2 trigonal bipyramid, edges with two equivalent SRb2Sb3 square pyramids, an edgeedge with one SRb3Sb2 trigonal bipyramid, and an edgeedge with one SRb2Sb2 trigonal pyramid. In the third S2- site, S2- is bonded to three Rb1+ and two Sb3+ atoms to form distorted SRb3Sb2 trigonal bipyramids that share corners with two equivalent SRb2Sb3 square pyramids, corners with six SRb2Sb2 tetrahedra, a cornercorner with one SRb2Sb2 trigonal pyramid, an edgeedge with one SRb2Sb3 square pyramid, an edgeedge with one SRb2Sb2 tetrahedra, an edgeedge with one SRb3Sb2 trigonal bipyramid, and an edgeedge with one SRb2Sb2 trigonal pyramid. In the fourth S2- site, S2- is bonded to two equivalent Rb1+ and two equivalent Sb3+ atoms to form distorted SRb2Sb2 tetrahedra that share corners with two equivalent SRb2Sb3 square pyramids, corners with two equivalent SRb2Sb2 tetrahedra, corners with four equivalent SRb3Sb2 trigonal bipyramids, and edges with two equivalent SRb2Sb2 tetrahedra. In the fifth S2- site, S2- is bonded in a 2-coordinate geometry to one Rb1+ and two Sb3+ atoms. In the sixth S2- site, S2- is bonded to two Rb1+ and three Sb3+ atoms to form distorted SRb2Sb3 square pyramids that share corners with four SRb2Sb2 tetrahedra, corners with two equivalent SRb3Sb2 trigonal bipyramids, a cornercorner with one SRb2Sb2 trigonal pyramid, an edgeedge with one SRb2Sb3 square pyramid, an edgeedge with one SRb2Sb2 tetrahedra, an edgeedge with one SRb3Sb2 trigonal bipyramid, and edges with two equivalent SRb2Sb2 trigonal pyramids. In the seventh S2- site, S2- is bonded to two Rb1+ and two Sb3+ atoms to form distorted SRb2Sb2 tetrahedra that share corners with two equivalent SRb2Sb3 square pyramids, corners with two equivalent SRb2Sb2 tetrahedra, corners with two equivalent SRb3Sb2 trigonal bipyramids, corners with three equivalent SRb2Sb2 trigonal pyramids, an edgeedge with one SRb2Sb3 square pyramid, and an edgeedge with one SRb3Sb2 trigonal bipyramid.