DOI: 10.17188/1727708
title: Materials Data on Er2MgSe4 by Materials Project

description: MgEr2Se4 crystallizes in the triclinic P-1 space group. The structure is two-dimensional and consists of one MgEr2Se4 sheet oriented in the (0, 0, 1) direction. there are two inequivalent Mg2+ sites. In the first Mg2+ site, Mg2+ is bonded to four Se2- atoms to form MgSe4 tetrahedra that share a cornercorner with one MgSe6 octahedra, corners with two equivalent ErSe6 octahedra, and corners with six ErSe4 tetrahedra. The corner-sharing octahedra tilt angles range from 59–60°. There are a spread of Mg–Se bond distances ranging from 2.57–2.61 Å. In the second Mg2+ site, Mg2+ is bonded to six Se2- atoms to form MgSe6 octahedra that share a cornercorner with one MgSe4 tetrahedra, corners with five ErSe4 tetrahedra, edges with two equivalent MgSe6 octahedra, and edges with four equivalent ErSe6 octahedra. There are a spread of Mg–Se bond distances ranging from 2.80–2.85 Å. There are four inequivalent Er3+ sites. In the first Er3+ site, Er3+ is bonded to four Se2- atoms to form ErSe4 tetrahedra that share a cornercorner with one ErSe6 octahedra, corners with two equivalent MgSe6 octahedra, corners with two equivalent MgSe4 tetrahedra, and corners with four ErSe4 tetrahedra. The corner-sharing octahedra tilt angles range from 58–62°. There are a spread of Er–Se bond distances ranging from 2.68–2.72 Å. In the second Er3+ site, Er3+ is bonded to six Se2- atoms to form ErSe6 octahedra that share corners with two equivalent MgSe4 tetrahedra, corners with four ErSe4 tetrahedra, edges with two equivalent ErSe6 octahedra, and edges with four equivalent MgSe6 octahedra. There are a spread of Er–Se bond distances ranging from 2.85–2.92 Å. In the third Er3+ site, Er3+ is bonded to four Se2- atoms to form ErSe4 tetrahedra that share a cornercorner with one ErSe6 octahedra, corners with two equivalent MgSe6 octahedra, corners with two equivalent MgSe4 tetrahedra, and corners with four ErSe4 tetrahedra. The corner-sharing octahedra tilt angles range from 58–63°. There are a spread of Er–Se bond distances ranging from 2.68–2.72 Å. In the fourth Er3+ site, Er3+ is bonded to four Se2- atoms to form ErSe4 tetrahedra that share a cornercorner with one MgSe6 octahedra, corners with two equivalent ErSe6 octahedra, corners with two equivalent MgSe4 tetrahedra, and corners with four ErSe4 tetrahedra. The corner-sharing octahedra tilt angles range from 58–62°. There are a spread of Er–Se bond distances ranging from 2.69–2.72 Å. There are eight inequivalent Se2- sites. In the first Se2- site, Se2- is bonded to two equivalent Mg2+ and two Er3+ atoms to form distorted SeEr2Mg2 tetrahedra that share corners with seven SeEr3Mg tetrahedra, corners with two equivalent SeEr2Mg2 trigonal pyramids, edges with two SeEr2Mg2 tetrahedra, and an edgeedge with one SeEr2Mg2 trigonal pyramid. In the second Se2- site, Se2- is bonded to two Mg2+ and two equivalent Er3+ atoms to form distorted SeEr2Mg2 trigonal pyramids that share corners with nine SeEr2Mg2 tetrahedra, edges with two SeEr3Mg tetrahedra, and an edgeedge with one SeEr2Mg2 trigonal pyramid. In the third Se2- site, Se2- is bonded in a trigonal non-coplanar geometry to one Mg2+ and two Er3+ atoms. In the fourth Se2- site, Se2- is bonded in a trigonal non-coplanar geometry to three Er3+ atoms. In the fifth Se2- site, Se2- is bonded in a trigonal non-coplanar geometry to one Mg2+ and two Er3+ atoms. In the sixth Se2- site, Se2- is bonded in a trigonal non-coplanar geometry to one Mg2+ and two Er3+ atoms. In the seventh Se2- site, Se2- is bonded to one Mg2+ and three Er3+ atoms to form distorted SeEr3Mg tetrahedra that share corners with six SeEr2Mg2 tetrahedra, corners with three equivalent SeEr2Mg2 trigonal pyramids, edges with two SeEr3Mg tetrahedra, and an edgeedge with one SeEr2Mg2 trigonal pyramid. In the eighth Se2- site, Se2- is bonded to two equivalent Mg2+ and two Er3+ atoms to form distorted SeEr2Mg2 tetrahedra that share corners with five SeEr2Mg2 tetrahedra, corners with four equivalent SeEr2Mg2 trigonal pyramids, and edges with three SeEr3Mg tetrahedra.