DOI: 10.17188/1737337
title: Materials Data on Er2MgS4 by Materials Project

description: MgEr2S4 crystallizes in the triclinic P-1 space group. The structure is two-dimensional and consists of one MgEr2S4 sheet oriented in the (0, 0, 1) direction. there are two inequivalent Mg2+ sites. In the first Mg2+ site, Mg2+ is bonded to four S2- atoms to form MgS4 tetrahedra that share a cornercorner with one MgS6 octahedra, corners with two equivalent ErS6 octahedra, and corners with six ErS4 tetrahedra. The corner-sharing octahedra tilt angles range from 59–60°. There are a spread of Mg–S bond distances ranging from 2.44–2.48 Å. In the second Mg2+ site, Mg2+ is bonded to six S2- atoms to form MgS6 octahedra that share a cornercorner with one MgS4 tetrahedra, corners with five ErS4 tetrahedra, edges with two equivalent MgS6 octahedra, and edges with four equivalent ErS6 octahedra. There are a spread of Mg–S bond distances ranging from 2.68–2.73 Å. There are four inequivalent Er3+ sites. In the first Er3+ site, Er3+ is bonded to four S2- atoms to form ErS4 tetrahedra that share a cornercorner with one ErS6 octahedra, corners with two equivalent MgS6 octahedra, corners with two equivalent MgS4 tetrahedra, and corners with four ErS4 tetrahedra. The corner-sharing octahedra tilt angles range from 59–62°. There are a spread of Er–S bond distances ranging from 2.54–2.59 Å. In the second Er3+ site, Er3+ is bonded to six S2- atoms to form ErS6 octahedra that share corners with two equivalent MgS4 tetrahedra, corners with four ErS4 tetrahedra, edges with two equivalent ErS6 octahedra, and edges with four equivalent MgS6 octahedra. There are a spread of Er–S bond distances ranging from 2.73–2.80 Å. In the third Er3+ site, Er3+ is bonded to four S2- atoms to form ErS4 tetrahedra that share a cornercorner with one ErS6 octahedra, corners with two equivalent MgS6 octahedra, corners with two equivalent MgS4 tetrahedra, and corners with four ErS4 tetrahedra. The corner-sharing octahedra tilt angles range from 59–64°. There are a spread of Er–S bond distances ranging from 2.54–2.59 Å. In the fourth Er3+ site, Er3+ is bonded to four S2- atoms to form ErS4 tetrahedra that share a cornercorner with one MgS6 octahedra, corners with two equivalent ErS6 octahedra, corners with two equivalent MgS4 tetrahedra, and corners with four ErS4 tetrahedra. The corner-sharing octahedra tilt angles range from 58–62°. There are a spread of Er–S bond distances ranging from 2.55–2.58 Å. There are eight inequivalent S2- sites. In the first S2- site, S2- is bonded to two equivalent Mg2+ and two Er3+ atoms to form distorted SEr2Mg2 tetrahedra that share corners with seven SEr3Mg tetrahedra, corners with two equivalent SEr2Mg2 trigonal pyramids, edges with two SEr2Mg2 tetrahedra, and an edgeedge with one SEr2Mg2 trigonal pyramid. In the second S2- site, S2- is bonded to two Mg2+ and two equivalent Er3+ atoms to form distorted SEr2Mg2 trigonal pyramids that share corners with nine SEr2Mg2 tetrahedra, edges with two SEr3Mg tetrahedra, and an edgeedge with one SEr2Mg2 trigonal pyramid. In the third S2- site, S2- is bonded in a trigonal non-coplanar geometry to one Mg2+ and two Er3+ atoms. In the fourth S2- site, S2- is bonded in a trigonal non-coplanar geometry to three Er3+ atoms. In the fifth S2- site, S2- is bonded in a trigonal non-coplanar geometry to one Mg2+ and two Er3+ atoms. In the sixth S2- site, S2- is bonded in a trigonal non-coplanar geometry to one Mg2+ and two Er3+ atoms. In the seventh S2- site, S2- is bonded to one Mg2+ and three Er3+ atoms to form distorted SEr3Mg tetrahedra that share corners with six SEr2Mg2 tetrahedra, corners with three equivalent SEr2Mg2 trigonal pyramids, edges with two SEr3Mg tetrahedra, and an edgeedge with one SEr2Mg2 trigonal pyramid. In the eighth S2- site, S2- is bonded to two equivalent Mg2+ and two Er3+ atoms to form distorted SEr2Mg2 tetrahedra that share corners with five SEr2Mg2 tetrahedra, corners with four equivalent SEr2Mg2 trigonal pyramids, and edges with three SEr3Mg tetrahedra.