DOI: 10.17188/1654474
title: Materials Data on Er4CrSe7 by Materials Project

description: Er4CrSe7 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 to seven Se2- atoms to form distorted ErSe7 pentagonal bipyramids that share corners with four ErSe6 octahedra, corners with four equivalent CrSe6 octahedra, an edgeedge with one CrSe6 octahedra, edges with three equivalent ErSe6 octahedra, edges with two equivalent ErSe7 pentagonal bipyramids, and faces with two equivalent ErSe7 pentagonal bipyramids. The corner-sharing octahedra tilt angles range from 18–75°. There are a spread of Er–Se bond distances ranging from 2.86–3.20 Å. In the second Er3+ site, Er3+ is bonded to seven Se2- atoms to form distorted ErSe7 pentagonal bipyramids that share corners with two equivalent CrSe6 octahedra, corners with six ErSe6 octahedra, edges with four ErSe6 octahedra, edges with two equivalent ErSe7 pentagonal bipyramids, and faces with two equivalent ErSe7 pentagonal bipyramids. The corner-sharing octahedra tilt angles range from 22–67°. There are a spread of Er–Se bond distances ranging from 2.83–3.09 Å. In the third Er3+ site, Er3+ is bonded to six Se2- atoms to form ErSe6 octahedra that share a cornercorner with one ErSe6 octahedra, a cornercorner with one CrSe6 octahedra, corners with four ErSe7 pentagonal bipyramids, edges with two equivalent ErSe6 octahedra, and edges with six ErSe7 pentagonal bipyramids. The corner-sharing octahedra tilt angles range from 50–53°. There are a spread of Er–Se bond distances ranging from 2.79–2.83 Å. In the fourth Er3+ site, Er3+ is bonded to six Se2- atoms to form ErSe6 octahedra that share a cornercorner with one ErSe6 octahedra, corners with two equivalent CrSe6 octahedra, corners with six ErSe7 pentagonal bipyramids, edges with two equivalent ErSe6 octahedra, edges with three equivalent CrSe6 octahedra, and an edgeedge with one ErSe7 pentagonal bipyramid. The corner-sharing octahedra tilt angles range from 3–50°. There are a spread of Er–Se bond distances ranging from 2.78–2.90 Å. Cr2+ is bonded to six Se2- atoms to form CrSe6 octahedra that share corners with three ErSe6 octahedra, corners with six ErSe7 pentagonal bipyramids, edges with two equivalent CrSe6 octahedra, edges with three equivalent ErSe6 octahedra, and an edgeedge with one ErSe7 pentagonal bipyramid. The corner-sharing octahedra tilt angles range from 3–53°. There are a spread of Cr–Se bond distances ranging from 2.60–2.73 Å. There are seven inequivalent Se2- sites. In the first Se2- site, Se2- is bonded to four Er3+ and one Cr2+ atom to form distorted SeEr4Cr trigonal bipyramids that share corners with five SeEr3Cr tetrahedra, corners with two equivalent SeEr5 trigonal bipyramids, an edgeedge with one SeEr4 tetrahedra, and edges with four SeEr4Cr trigonal bipyramids. In the second Se2- site, Se2- is bonded to three Er3+ and two equivalent Cr2+ atoms to form distorted SeEr3Cr2 trigonal bipyramids that share corners with five SeEr3Cr tetrahedra, corners with two equivalent SeEr5 trigonal bipyramids, an edgeedge with one SeEr3Cr tetrahedra, and edges with five SeEr4Cr trigonal bipyramids. In the third Se2- site, Se2- is bonded to five Er3+ atoms to form distorted SeEr5 trigonal bipyramids that share corners with four equivalent SeEr3Cr tetrahedra, corners with four SeEr4Cr trigonal bipyramids, edges with three SeEr3Cr tetrahedra, and edges with three SeEr3Cr2 trigonal bipyramids. In the fourth Se2- site, Se2- is bonded in a 5-coordinate geometry to five Er3+ atoms. In the fifth Se2- site, Se2- is bonded to three Er3+ and one Cr2+ atom to form distorted SeEr3Cr tetrahedra that share corners with three SeEr3Cr tetrahedra, corners with nine SeEr4Cr trigonal bipyramids, and edges with two SeEr3Cr2 trigonal bipyramids. In the sixth Se2- site, Se2- is bonded to four Er3+ atoms to form distorted SeEr4 tetrahedra that share corners with three SeEr3Cr tetrahedra, corners with five SeEr4Cr trigonal bipyramids, and edges with three SeEr4Cr trigonal bipyramids. In the seventh Se2- site, Se2- is bonded in a rectangular see-saw-like geometry to two equivalent Er3+ and two equivalent Cr2+ atoms.