Materials Data on Er2MgSe4 by Materials Project

Abstract

MgEr2Se4 crystallizes in the orthorhombic Pnma space group. The structure is three-dimensional. Mg2+ is bonded to five Se2- atoms to form MgSe5 square pyramids that share corners with four ErSe6 octahedra, edges with four ErSe6 octahedra, and edges with four equivalent MgSe5 square pyramids. The corner-sharing octahedra tilt angles range from 6–11°. There are three shorter (2.75 Å) and two longer (2.81 Å) Mg–Se bond lengths. There are two inequivalent Er3+ sites. In the first Er3+ site, Er3+ is bonded to six Se2- atoms to form ErSe6 octahedra that share corners with three equivalent ErSe6 octahedra, corners with two equivalent MgSe5 square pyramids, edges with six ErSe6 octahedra, and an edgeedge with one MgSe5 square pyramid. The corner-sharing octahedra tilt angles range from 52–59°. There are a spread of Er–Se bond distances ranging from 2.82–2.92 Å. In the second Er3+ site, Er3+ is bonded to six Se2- atoms to form ErSe6 octahedra that share corners with three equivalent ErSe6 octahedra, corners with two equivalent MgSe5 square pyramids, edges with four ErSe6 octahedra, and edges with three equivalent MgSe5 square pyramids. The corner-sharing octahedra tilt angles range from 52–59°. There are a spread of Er–Se bond distances ranging from 2.78–2.90 Å. There are four inequivalent Se2- sites. In the first Se2- site, Se2- is bonded to three equivalent Mg2+ and two equivalent Er3+ atoms to form a mixture of edge and corner-sharing SeEr2Mg3 square pyramids. In the second Se2- site, Se2- is bonded in a rectangular see-saw-like geometry to four Er3+ atoms. In the third Se2- site, Se2- is bonded in a distorted T-shaped geometry to three Er3+ atoms. In the fourth Se2- site, Se2- is bonded to two equivalent Mg2+ and three Er3+ atoms to form SeEr3Mg2 square pyramids that share corners with two equivalent SeEr2Mg3 square pyramids and edges with five SeEr3Mg2 square pyramids.