DOI: 10.17188/1318590
title: Materials Data on Mg(FeO2)2 by Materials Project

description: MgFe2O4 crystallizes in the monoclinic Cm space group. The structure is three-dimensional. there are two inequivalent Mg2+ sites. In the first Mg2+ site, Mg2+ is bonded to five O2- atoms to form MgO5 trigonal bipyramids that share corners with four FeO6 octahedra, corners with four FeO5 trigonal bipyramids, an edgeedge with one FeO5 trigonal bipyramid, edges with two equivalent MgO5 trigonal bipyramids, and a faceface with one FeO6 octahedra. The corner-sharing octahedra tilt angles range from 40–61°. There are two shorter (2.04 Å) and three longer (2.08 Å) Mg–O bond lengths. In the second Mg2+ site, Mg2+ is bonded to five O2- atoms to form MgO5 trigonal bipyramids that share corners with four FeO6 octahedra, corners with four FeO5 trigonal bipyramids, an edgeedge with one FeO5 trigonal bipyramid, edges with two equivalent MgO5 trigonal bipyramids, and a faceface with one FeO6 octahedra. The corner-sharing octahedra tilt angles range from 40–60°. There are two shorter (2.04 Å) and three longer (2.08 Å) Mg–O bond lengths. There are four inequivalent Fe3+ sites. In the first Fe3+ site, Fe3+ is bonded to five O2- atoms to form distorted FeO5 trigonal bipyramids that share corners with four FeO6 octahedra, corners with four MgO5 trigonal bipyramids, an edgeedge with one MgO5 trigonal bipyramid, and edges with two equivalent FeO5 trigonal bipyramids. The corner-sharing octahedral tilt angles are 51°. There are a spread of Fe–O bond distances ranging from 1.93–2.06 Å. In the second Fe3+ site, Fe3+ is bonded to six O2- atoms to form FeO6 octahedra that share corners with four MgO5 trigonal bipyramids, corners with four FeO5 trigonal bipyramids, edges with four FeO6 octahedra, and a faceface with one MgO5 trigonal bipyramid. There are a spread of Fe–O bond distances ranging from 1.95–2.18 Å. In the third Fe3+ site, Fe3+ is bonded to six O2- atoms to form FeO6 octahedra that share corners with four MgO5 trigonal bipyramids, corners with four FeO5 trigonal bipyramids, edges with four FeO6 octahedra, and a faceface with one MgO5 trigonal bipyramid. There are a spread of Fe–O bond distances ranging from 1.95–2.18 Å. In the fourth Fe3+ site, Fe3+ is bonded to five O2- atoms to form distorted FeO5 trigonal bipyramids that share corners with four FeO6 octahedra, corners with four MgO5 trigonal bipyramids, an edgeedge with one MgO5 trigonal bipyramid, and edges with two equivalent FeO5 trigonal bipyramids. The corner-sharing octahedral tilt angles are 51°. There are a spread of Fe–O bond distances ranging from 1.92–2.07 Å. There are eight inequivalent O2- sites. In the first O2- site, O2- is bonded to one Mg2+ and three Fe3+ atoms to form distorted OMgFe3 tetrahedra that share corners with two equivalent OMgFe3 tetrahedra, a cornercorner with one OMg2Fe3 trigonal bipyramid, and edges with two equivalent OMg2Fe3 trigonal bipyramids. In the second O2- site, O2- is bonded in a distorted trigonal planar geometry to three Fe3+ atoms. In the third O2- site, O2- is bonded in a distorted trigonal planar geometry to three Fe3+ atoms. In the fourth O2- site, O2- is bonded to one Mg2+ and three Fe3+ atoms to form distorted OMgFe3 tetrahedra that share corners with two equivalent OMgFe3 tetrahedra, a cornercorner with one OMg2Fe3 trigonal bipyramid, and edges with two equivalent OMg2Fe3 trigonal bipyramids. In the fifth O2- site, O2- is bonded in a rectangular see-saw-like geometry to two equivalent Mg2+ and two equivalent Fe3+ atoms. In the sixth O2- site, O2- is bonded to two equivalent Mg2+ and three Fe3+ atoms to form distorted OMg2Fe3 trigonal bipyramids that share a cornercorner with one OMgFe3 tetrahedra, edges with two equivalent OMgFe3 tetrahedra, and edges with four OMg2Fe3 trigonal bipyramids. In the seventh O2- site, O2- is bonded in a rectangular see-saw-like geometry to two equivalent Mg2+ and two equivalent Fe3+ atoms. In the eighth O2- site, O2- is bonded to two equivalent Mg2+ and three Fe3+ atoms to form distorted OMg2Fe3 trigonal bipyramids that share a cornercorner with one OMgFe3 tetrahedra, edges with two equivalent OMgFe3 tetrahedra, and edges with four OMg2Fe3 trigonal bipyramids.