DOI: 10.17188/1654287
title: Materials Data on Eu2MgSe4 by Materials Project

description: MgEu2Se4 crystallizes in the orthorhombic Pca2_1 space group. The structure is three-dimensional. there are two inequivalent Mg2+ sites. In the first Mg2+ site, Mg2+ is bonded to six Se2- atoms to form MgSe6 octahedra that share a cornercorner with one EuSe6 octahedra, corners with two equivalent MgSe6 octahedra, corners with four EuSe7 pentagonal bipyramids, an edgeedge with one MgSe6 octahedra, edges with four EuSe6 octahedra, and edges with three EuSe7 pentagonal bipyramids. The corner-sharing octahedra tilt angles range from 9–56°. There are a spread of Mg–Se bond distances ranging from 2.62–2.97 Å. In the second Mg2+ site, Mg2+ is bonded to six Se2- atoms to form MgSe6 octahedra that share a cornercorner with one EuSe6 octahedra, corners with two equivalent MgSe6 octahedra, corners with four EuSe7 pentagonal bipyramids, an edgeedge with one MgSe6 octahedra, edges with four EuSe6 octahedra, and edges with three EuSe7 pentagonal bipyramids. The corner-sharing octahedra tilt angles range from 9–56°. There are a spread of Mg–Se bond distances ranging from 2.60–2.93 Å. There are four inequivalent Eu3+ sites. In the first Eu3+ site, Eu3+ is bonded to six Se2- atoms to form EuSe6 octahedra that share a cornercorner with one MgSe6 octahedra, corners with two equivalent EuSe6 octahedra, corners with four EuSe7 pentagonal bipyramids, an edgeedge with one EuSe6 octahedra, edges with four MgSe6 octahedra, and edges with three EuSe7 pentagonal bipyramids. The corner-sharing octahedra tilt angles range from 10–56°. There are a spread of Eu–Se bond distances ranging from 2.86–2.97 Å. In the second Eu3+ site, Eu3+ is bonded to six Se2- atoms to form EuSe6 octahedra that share a cornercorner with one MgSe6 octahedra, corners with two equivalent EuSe6 octahedra, corners with four EuSe7 pentagonal bipyramids, an edgeedge with one EuSe6 octahedra, edges with four MgSe6 octahedra, and edges with three EuSe7 pentagonal bipyramids. The corner-sharing octahedra tilt angles range from 10–56°. There are a spread of Eu–Se bond distances ranging from 2.88–2.97 Å. In the third Eu3+ site, Eu3+ is bonded to seven Se2- atoms to form distorted EuSe7 pentagonal bipyramids that share corners with four MgSe6 octahedra, corners with four EuSe6 octahedra, edges with three MgSe6 octahedra, edges with three EuSe6 octahedra, and faces with two equivalent EuSe7 pentagonal bipyramids. The corner-sharing octahedra tilt angles range from 11–74°. There are a spread of Eu–Se bond distances ranging from 2.97–3.17 Å. In the fourth Eu3+ site, Eu3+ is bonded to seven Se2- atoms to form distorted EuSe7 pentagonal bipyramids that share corners with four MgSe6 octahedra, corners with four EuSe6 octahedra, edges with three MgSe6 octahedra, edges with three EuSe6 octahedra, and faces with two equivalent EuSe7 pentagonal bipyramids. The corner-sharing octahedra tilt angles range from 13–76°. There are a spread of Eu–Se bond distances ranging from 2.95–3.21 Å. There are eight inequivalent Se2- sites. In the first Se2- site, Se2- is bonded to two Mg2+ and three Eu3+ atoms to form distorted SeEu3Mg2 square pyramids that share corners with two equivalent SeEu3Mg2 square pyramids, corners with three equivalent SeEu3Mg tetrahedra, edges with five SeEu3Mg2 square pyramids, and edges with two equivalent SeEu4Mg trigonal bipyramids. In the second Se2- site, Se2- is bonded in a 5-coordinate geometry to two Mg2+ and three Eu3+ atoms. In the third Se2- site, Se2- is bonded to one Mg2+ and three Eu3+ atoms to form distorted SeEu3Mg tetrahedra that share corners with seven SeEu3Mg2 square pyramids, corners with three equivalent SeEu4Mg trigonal bipyramids, and edges with three SeEu3Mg2 square pyramids. In the fourth Se2- site, Se2- is bonded in a distorted rectangular see-saw-like geometry to one Mg2+ and three Eu3+ atoms. In the fifth Se2- site, Se2- is bonded to two Mg2+ and three Eu3+ atoms to form SeEu3Mg2 square pyramids that share corners with two equivalent SeEu3Mg2 square pyramids, a cornercorner with one SeEu3Mg tetrahedra, corners with four equivalent SeEu4Mg trigonal bipyramids, edges with five SeEu3Mg2 square pyramids, and an edgeedge with one SeEu3Mg tetrahedra. In the sixth Se2- site, Se2- is bonded to two Mg2+ and three Eu3+ atoms to form SeEu3Mg2 square pyramids that share corners with two equivalent SeEu4Mg square pyramids, a cornercorner with one SeEu3Mg tetrahedra, corners with two equivalent SeEu4Mg trigonal bipyramids, edges with five SeEu3Mg2 square pyramids, an edgeedge with one SeEu3Mg tetrahedra, and an edgeedge with one SeEu4Mg trigonal bipyramid. In the seventh Se2- site, Se2- is bonded to one Mg2+ and four Eu3+ atoms to form SeEu4Mg square pyramids that share corners with two equivalent SeEu3Mg2 square pyramids, corners with two equivalent SeEu3Mg tetrahedra, corners with two equivalent SeEu4Mg trigonal bipyramids, edges with five SeEu3Mg2 square pyramids, an edgeedge with one SeEu3Mg tetrahedra, and an edgeedge with one SeEu4Mg trigonal bipyramid. In the eighth Se2- site, Se2- is bonded to one Mg2+ and four Eu3+ atoms to form distorted SeEu4Mg trigonal bipyramids that share corners with eight SeEu3Mg2 square pyramids, corners with three equivalent SeEu3Mg tetrahedra, and edges with four SeEu3Mg2 square pyramids.