DOE OSTI2020
Yb(TmS2)2 crystallizes in the orthorhombic Pnma space group. The structure is three-dimensional. Yb2+ is bonded to seven S2- atoms to form distorted YbS7 pentagonal bipyramids that share corners with eight TmS6 octahedra, edges with five TmS6 octahedra, edges with two equivalent YbS7 pentagonal bipyramids, and faces with two equivalent YbS7 pentagonal bipyramids. The corner-sharing octahedra tilt angles range from 14–67°. There are a spread of Yb–S bond distances ranging from 2.86–2.98 Å. There are two inequivalent Tm3+ sites. In the first Tm3+ site, Tm3+ is bonded to six S2- atoms to form TmS6 octahedra that share corners with three equivalent TmS6 octahedra, corners with four equivalent YbS7 pentagonal bipyramids, edges with six TmS6 octahedra, and an edgeedge with one YbS7 pentagonal bipyramid. The corner-sharing octahedra tilt angles range from 52–60°. There are a spread of Tm–S bond distances ranging from 2.68–2.78 Å. In the second Tm3+ site, Tm3+ is bonded to six S2- atoms to form TmS6 octahedra that share corners with three equivalent TmS6 octahedra, corners with four equivalent YbS7 pentagonal bipyramids, edges with four TmS6 octahedra, and edges with four equivalent YbS7 pentagonal bipyramids. The corner-sharing octahedra tilt angles range from 52–60°. There are a spread of Tm–S bond distances ranging from 2.67–2.75 Å. There are four inequivalent S2- sites. In the first S2- site, S2- is bonded to two equivalent Yb2+ and three Tm3+ atoms to form a mixture of distorted edge and corner-sharing SYb2Tm3 trigonal bipyramids. In the second S2- site, S2- is bonded to two equivalent Yb2+ and three Tm3+ atoms to form SYb2Tm3 square pyramids that share corners with two equivalent SYb3Tm2 square pyramids, corners with two equivalent SYb2Tm3 trigonal bipyramids, edges with five SYb2Tm3 square pyramids, and edges with three equivalent SYb2Tm3 trigonal bipyramids. In the third S2- site, S2- is bonded to three equivalent Yb2+ and two equivalent Tm3+ atoms to form a mixture of distorted edge and corner-sharing SYb3Tm2 square pyramids. In the fourth S2- site, S2- is bonded in a rectangular see-saw-like geometry to four Tm3+ atoms.