DOI: 10.17188/1754405
title: Materials Data on Tm4CrSe7 by Materials Project

description: Tm4CrSe7 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 in a 7-coordinate geometry to seven Se2- atoms. There are a spread of Tm–Se bond distances ranging from 2.83–3.19 Å. In the second Tm3+ site, Tm3+ is bonded to seven Se2- atoms to form distorted TmSe7 pentagonal bipyramids that share corners with two equivalent CrSe6 octahedra, corners with six TmSe6 octahedra, edges with four TmSe6 octahedra, and faces with two equivalent TmSe7 pentagonal bipyramids. The corner-sharing octahedra tilt angles range from 22–68°. There are a spread of Tm–Se bond distances ranging from 2.80–3.07 Å. In the third Tm3+ site, Tm3+ is bonded to six Se2- atoms to form TmSe6 octahedra that share a cornercorner with one TmSe6 octahedra, a cornercorner with one CrSe6 octahedra, corners with two equivalent TmSe7 pentagonal bipyramids, edges with two equivalent TmSe6 octahedra, and edges with three equivalent TmSe7 pentagonal bipyramids. The corner-sharing octahedra tilt angles range from 50–54°. There are a spread of Tm–Se bond distances ranging from 2.78–2.81 Å. In the fourth Tm3+ site, Tm3+ is bonded to six Se2- atoms to form TmSe6 octahedra that share a cornercorner with one TmSe6 octahedra, corners with two equivalent CrSe6 octahedra, corners with four equivalent TmSe7 pentagonal bipyramids, edges with two equivalent TmSe6 octahedra, edges with three equivalent CrSe6 octahedra, and an edgeedge with one TmSe7 pentagonal bipyramid. The corner-sharing octahedra tilt angles range from 2–50°. There are a spread of Tm–Se bond distances ranging from 2.76–2.88 Å. Cr2+ is bonded to six Se2- atoms to form CrSe6 octahedra that share corners with three TmSe6 octahedra, corners with two equivalent TmSe7 pentagonal bipyramids, edges with two equivalent CrSe6 octahedra, and edges with three equivalent TmSe6 octahedra. The corner-sharing octahedra tilt angles range from 2–54°. There are a spread of Cr–Se bond distances ranging from 2.58–2.73 Å. There are seven inequivalent Se2- sites. In the first Se2- site, Se2- is bonded to four Tm3+ and one Cr2+ atom to form distorted SeTm4Cr trigonal bipyramids that share corners with five SeTm3Cr tetrahedra, corners with two equivalent SeTm5 trigonal bipyramids, edges with two equivalent SeTm3Cr2 square pyramids, an edgeedge with one SeTm4 tetrahedra, and edges with two equivalent SeTm4Cr trigonal bipyramids. In the second Se2- site, Se2- is bonded to three Tm3+ and two equivalent Cr2+ atoms to form distorted SeTm3Cr2 square pyramids that share corners with five SeTm3Cr tetrahedra, corners with two equivalent SeTm5 trigonal bipyramids, edges with two equivalent SeTm3Cr2 square pyramids, an edgeedge with one SeTm3Cr tetrahedra, and edges with three SeTm4Cr trigonal bipyramids. In the third Se2- site, Se2- is bonded to five Tm3+ atoms to form distorted SeTm5 trigonal bipyramids that share corners with two equivalent SeTm3Cr2 square pyramids, corners with four equivalent SeTm3Cr tetrahedra, corners with two equivalent SeTm4Cr trigonal bipyramids, an edgeedge with one SeTm3Cr2 square pyramid, edges with three SeTm3Cr tetrahedra, and edges with two equivalent SeTm5 trigonal bipyramids. In the fourth Se2- site, Se2- is bonded in a 5-coordinate geometry to five Tm3+ atoms. In the fifth Se2- site, Se2- is bonded to three Tm3+ and one Cr2+ atom to form distorted SeTm3Cr tetrahedra that share corners with four equivalent SeTm3Cr2 square pyramids, corners with three SeTm3Cr tetrahedra, corners with five SeTm4Cr trigonal bipyramids, an edgeedge with one SeTm3Cr2 square pyramid, and an edgeedge with one SeTm5 trigonal bipyramid. In the sixth Se2- site, Se2- is bonded to four Tm3+ atoms to form distorted SeTm4 tetrahedra that share a cornercorner with one SeTm3Cr2 square pyramid, corners with three SeTm3Cr tetrahedra, corners with four equivalent SeTm4Cr trigonal bipyramids, and edges with three SeTm4Cr trigonal bipyramids. In the seventh Se2- site, Se2- is bonded in a rectangular see-saw-like geometry to two equivalent Tm3+ and two equivalent Cr2+ atoms.