DOI: 10.17188/1722112
title: Materials Data on Tm4MgS7 by Materials Project

description: MgTm4S7 crystallizes in the monoclinic Cm space group. The structure is three-dimensional. Mg2+ is bonded to six S2- atoms to form MgS6 octahedra that share corners with three TmS6 octahedra, corners with six TmS7 pentagonal bipyramids, edges with two equivalent MgS6 octahedra, edges with three equivalent TmS6 octahedra, and an edgeedge with one TmS7 pentagonal bipyramid. The corner-sharing octahedra tilt angles range from 2–55°. There are a spread of Mg–S bond distances ranging from 2.55–2.68 Å. 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 equivalent MgS6 octahedra, corners with four TmS6 octahedra, an edgeedge with one MgS6 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 20–73°. There are a spread of Tm–S bond distances ranging from 2.68–3.03 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 MgS6 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 22–68°. There are a spread of Tm–S bond distances ranging from 2.67–2.95 Å. In the third Tm3+ site, Tm3+ is bonded to six S2- atoms to form TmS6 octahedra that share a cornercorner with one MgS6 octahedra, a cornercorner with one TmS6 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 53–55°. There are a spread of Tm–S bond distances ranging from 2.63–2.70 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 MgS6 octahedra, corners with six TmS7 pentagonal bipyramids, edges with two equivalent TmS6 octahedra, edges with three equivalent MgS6 octahedra, and an edgeedge with one TmS7 pentagonal bipyramid. The corner-sharing octahedra tilt angles range from 2–53°. There are a spread of Tm–S bond distances ranging from 2.63–2.74 Å. There are seven inequivalent S2- sites. In the first S2- site, S2- is bonded to one Mg2+ and four Tm3+ atoms to form distorted STm4Mg trigonal bipyramids that share corners with five STm3Mg tetrahedra, corners with four STm5 trigonal bipyramids, an edgeedge with one STm4 tetrahedra, and edges with five STm4Mg trigonal bipyramids. In the second S2- site, S2- is bonded to two equivalent Mg2+ and three Tm3+ atoms to form distorted STm3Mg2 trigonal bipyramids that share corners with five STm3Mg tetrahedra, corners with four STm5 trigonal bipyramids, an edgeedge with one STm3Mg tetrahedra, and edges with five STm4Mg 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 STm3Mg tetrahedra, corners with six STm4Mg trigonal bipyramids, edges with three STm3Mg tetrahedra, and edges with six STm3Mg2 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 STm4Mg trigonal bipyramids, edges with three STm3Mg tetrahedra, and edges with six STm4Mg trigonal bipyramids. In the fifth S2- site, S2- is bonded to one Mg2+ and three Tm3+ atoms to form distorted STm3Mg tetrahedra that share corners with three STm3Mg tetrahedra, corners with nine STm4Mg trigonal bipyramids, and edges with four STm3Mg2 trigonal bipyramids. In the sixth S2- site, S2- is bonded to four Tm3+ atoms to form distorted STm4 tetrahedra that share corners with three STm3Mg tetrahedra, corners with nine STm4Mg trigonal bipyramids, and edges with four STm4Mg trigonal bipyramids. In the seventh S2- site, S2- is bonded in a square co-planar geometry to two equivalent Mg2+ and two equivalent Tm3+ atoms.