DOE OSTI2020
Tm4CdS7 crystallizes in the monoclinic Cm space group. The structure is three-dimensional. there are four inequivalent Tm3+ sites. In the first Tm3+ site, Tm3+ is bonded to seven S2- atoms to form distorted TmS7 pentagonal bipyramids that share corners with four TmS6 octahedra, corners with four equivalent CdS6 octahedra, an edgeedge with one CdS6 octahedra, edges with three equivalent TmS6 octahedra, edges with two equivalent TmS7 pentagonal bipyramids, and faces with two equivalent TmS7 pentagonal bipyramids. The corner-sharing octahedra tilt angles range from 23–69°. There are a spread of Tm–S bond distances ranging from 2.68–3.01 Å. In the second Tm3+ site, Tm3+ is bonded to seven S2- atoms to form distorted TmS7 pentagonal bipyramids that share corners with two equivalent CdS6 octahedra, corners with six TmS6 octahedra, edges with four TmS6 octahedra, edges with two equivalent TmS7 pentagonal bipyramids, and faces with two equivalent TmS7 pentagonal bipyramids. The corner-sharing octahedra tilt angles range from 21–69°. There are a spread of Tm–S bond distances ranging from 2.68–2.95 Å. In the third Tm3+ site, Tm3+ is bonded to six S2- atoms to form TmS6 octahedra that share a cornercorner with one TmS6 octahedra, a cornercorner with one CdS6 octahedra, corners with four TmS7 pentagonal bipyramids, edges with two equivalent TmS6 octahedra, and edges with six TmS7 pentagonal bipyramids. The corner-sharing octahedra tilt angles range from 55–56°. There are a spread of Tm–S bond distances ranging from 2.63–2.71 Å. In the fourth Tm3+ site, Tm3+ is bonded to six S2- atoms to form TmS6 octahedra that share a cornercorner with one TmS6 octahedra, corners with two equivalent CdS6 octahedra, corners with six TmS7 pentagonal bipyramids, edges with two equivalent TmS6 octahedra, edges with three equivalent CdS6 octahedra, and an edgeedge with one TmS7 pentagonal bipyramid. The corner-sharing octahedra tilt angles range from 3–55°. There are a spread of Tm–S bond distances ranging from 2.62–2.75 Å. Cd2+ is bonded to six S2- atoms to form CdS6 octahedra that share corners with three TmS6 octahedra, corners with six TmS7 pentagonal bipyramids, edges with two equivalent CdS6 octahedra, edges with three equivalent TmS6 octahedra, and an edgeedge with one TmS7 pentagonal bipyramid. The corner-sharing octahedra tilt angles range from 3–56°. There are a spread of Cd–S bond distances ranging from 2.65–2.78 Å. There are seven inequivalent S2- sites. In the first S2- site, S2- is bonded to four Tm3+ and one Cd2+ atom to form distorted STm4Cd trigonal bipyramids that share corners with five STm3Cd tetrahedra, corners with four STm5 trigonal bipyramids, an edgeedge with one STm4 tetrahedra, and edges with five STm4Cd trigonal bipyramids. In the second S2- site, S2- is bonded to three Tm3+ and two equivalent Cd2+ atoms to form distorted STm3Cd2 trigonal bipyramids that share corners with five STm3Cd tetrahedra, corners with four STm5 trigonal bipyramids, an edgeedge with one STm3Cd tetrahedra, and edges with five STm4Cd trigonal bipyramids. In the third S2- site, S2- is bonded to five Tm3+ atoms to form distorted STm5 trigonal bipyramids that share corners with four equivalent STm3Cd tetrahedra, corners with six STm4Cd trigonal bipyramids, edges with three STm3Cd tetrahedra, and edges with six STm3Cd2 trigonal bipyramids. In the fourth S2- site, S2- is bonded to five Tm3+ atoms to form distorted STm5 trigonal bipyramids that share corners with four equivalent STm4 tetrahedra, corners with six STm4Cd trigonal bipyramids, edges with three STm3Cd tetrahedra, and edges with six STm4Cd trigonal bipyramids. In the fifth S2- site, S2- is bonded to three Tm3+ and one Cd2+ atom to form distorted STm3Cd tetrahedra that share corners with three STm3Cd tetrahedra, corners with nine STm4Cd trigonal bipyramids, and edges with four STm3Cd2 trigonal bipyramids. In the sixth S2- site, S2- is bonded to four Tm3+ atoms to form distorted STm4 tetrahedra that share corners with three STm3Cd tetrahedra, corners with nine STm4Cd trigonal bipyramids, and edges with four STm4Cd trigonal bipyramids. In the seventh S2- site, S2- is bonded in a rectangular see-saw-like geometry to two equivalent Tm3+ and two equivalent Cd2+ atoms.