Materials Data on Eu2MgSe4 by Materials Project
MgEu2Se4 is Spinel-like structured and crystallizes in the orthorhombic Pnma space group. The structure is three-dimensional. Mg2+ is bonded to four Se2- atoms to form MgSe4 tetrahedra that share corners with six EuSe6 octahedra and edges with three EuSe6 octahedra. The corner-sharing octahedra tilt angles range from 60–63°. There are one shorter (2.54 Å) and three longer (2.60 Å) Mg–Se bond lengths. There are two inequivalent Eu3+ sites. In the first Eu3+ site, Eu3+ is bonded to six Se2- atoms to form EuSe6 octahedra that share corners with four equivalent EuSe6 octahedra, corners with two equivalent MgSe4 tetrahedra, edges with four EuSe6 octahedra, and edges with two equivalent MgSe4 tetrahedra. The corner-sharing octahedra tilt angles range from 51–55°. There are a spread of Eu–Se bond distances ranging from 2.91–2.99 Å. In the second Eu3+ site, Eu3+ is bonded to six Se2- atoms to form EuSe6 octahedra that share corners with eight EuSe6 octahedra, corners with four equivalent MgSe4 tetrahedra, edges with two equivalent EuSe6 octahedra, and an edgeedge with one MgSe4 tetrahedra. The corner-sharing octahedra tilt angles range from 47–55°. There are a spread of Eu–Se bond distances ranging from 2.93–3.04 Å. There are three inequivalent Se2- sites. In the first Se2- site, Se2- is bonded in a rectangular see-saw-like geometry to one Mg2+ and three Eu3+ atoms. In the second Se2- site, Se2- is bonded in a rectangular see-saw-like geometry to one Mg2+ and three Eu3+ atoms. In the third Se2- site, Se2- is bonded to one Mg2+ and three Eu3+ atoms to form distorted corner-sharing SeEu3Mg tetrahedra.