DOI: 10.17188/1717542
title: Materials Data on Er4CrS7 by Materials Project

description: CrEr4S7 crystallizes in the monoclinic Cm space group. The structure is three-dimensional. there are four inequivalent Er3+ sites. In the first Er3+ site, Er3+ is bonded in a 7-coordinate geometry to seven S2- atoms. There are a spread of Er–S bond distances ranging from 2.72–3.05 Å. In the second Er3+ site, Er3+ is bonded to seven S2- atoms to form distorted ErS7 pentagonal bipyramids that share corners with two equivalent CrS6 octahedra, corners with six ErS6 octahedra, edges with four ErS6 octahedra, and faces with two equivalent ErS7 pentagonal bipyramids. The corner-sharing octahedra tilt angles range from 21–68°. There are a spread of Er–S bond distances ranging from 2.68–2.93 Å. In the third Er3+ site, Er3+ is bonded to six S2- atoms to form ErS6 octahedra that share a cornercorner with one ErS6 octahedra, a cornercorner with one CrS6 octahedra, corners with two equivalent ErS7 pentagonal bipyramids, edges with two equivalent ErS6 octahedra, and edges with three equivalent ErS7 pentagonal bipyramids. The corner-sharing octahedra tilt angles range from 51–54°. There are a spread of Er–S bond distances ranging from 2.65–2.70 Å. In the fourth Er3+ site, Er3+ is bonded to six S2- atoms to form ErS6 octahedra that share a cornercorner with one ErS6 octahedra, corners with two equivalent CrS6 octahedra, corners with four equivalent ErS7 pentagonal bipyramids, edges with two equivalent ErS6 octahedra, edges with three equivalent CrS6 octahedra, and an edgeedge with one ErS7 pentagonal bipyramid. The corner-sharing octahedra tilt angles range from 3–51°. There are a spread of Er–S bond distances ranging from 2.64–2.76 Å. Cr2+ is bonded to six S2- atoms to form CrS6 octahedra that share corners with three ErS6 octahedra, corners with two equivalent ErS7 pentagonal bipyramids, edges with two equivalent CrS6 octahedra, and edges with three equivalent ErS6 octahedra. The corner-sharing octahedra tilt angles range from 3–54°. There are a spread of Cr–S bond distances ranging from 2.44–2.61 Å. There are seven inequivalent S2- sites. In the first S2- site, S2- is bonded to four Er3+ and one Cr2+ atom to form distorted SEr4Cr trigonal bipyramids that share corners with five SEr3Cr tetrahedra, corners with four SEr5 trigonal bipyramids, edges with two equivalent SEr3Cr2 square pyramids, an edgeedge with one SEr4 tetrahedra, and edges with three SEr4Cr trigonal bipyramids. In the second S2- site, S2- is bonded to three Er3+ and two equivalent Cr2+ atoms to form distorted SEr3Cr2 square pyramids that share corners with five SEr3Cr tetrahedra, corners with four SEr5 trigonal bipyramids, edges with two equivalent SEr3Cr2 square pyramids, an edgeedge with one SEr3Cr tetrahedra, and edges with three SEr4Cr trigonal bipyramids. In the third S2- site, S2- is bonded to five Er3+ atoms to form distorted SEr5 trigonal bipyramids that share corners with two equivalent SEr3Cr2 square pyramids, corners with four equivalent SEr3Cr tetrahedra, corners with four SEr4Cr trigonal bipyramids, an edgeedge with one SEr3Cr2 square pyramid, edges with three SEr3Cr tetrahedra, and edges with five SEr5 trigonal bipyramids. In the fourth S2- site, S2- is bonded to five Er3+ atoms to form distorted SEr5 trigonal bipyramids that share corners with two equivalent SEr3Cr2 square pyramids, corners with four equivalent SEr4 tetrahedra, corners with four SEr4Cr trigonal bipyramids, edges with three SEr3Cr tetrahedra, and edges with six SEr4Cr trigonal bipyramids. In the fifth S2- site, S2- is bonded to three Er3+ and one Cr2+ atom to form distorted SEr3Cr tetrahedra that share corners with four equivalent SEr3Cr2 square pyramids, corners with three SEr3Cr tetrahedra, corners with five SEr4Cr trigonal bipyramids, an edgeedge with one SEr3Cr2 square pyramid, and edges with three SEr5 trigonal bipyramids. In the sixth S2- site, S2- is bonded to four Er3+ atoms to form distorted SEr4 tetrahedra that share a cornercorner with one SEr3Cr2 square pyramid, corners with three SEr3Cr tetrahedra, corners with eight SEr4Cr trigonal bipyramids, and edges with four SEr4Cr trigonal bipyramids. In the seventh S2- site, S2- is bonded in a rectangular see-saw-like geometry to two equivalent Er3+ and two equivalent Cr2+ atoms.