MgFe4(CoO4)2 crystallizes in the trigonal R-3m space group. Mg(1) is bonded to six equivalent O(1) atoms to form MgO6 octahedra that share corners with six equivalent Fe(2)O6 octahedra and edges with six equivalent Fe(1)O6 octahedra. The corner-sharing octahedral tilt angles are 3°. There are two inequivalent Fe sites. In the first Fe site, Fe(1) is bonded to two equivalent O(2) and four equivalent O(1) atoms to form FeO6 octahedra that share edges with two equivalent Mg(1)O6 octahedra, edges with two equivalent Fe(2)O6 octahedra, and edges with four equivalent Fe(1)O6 octahedra. In the second Fe site, Fe(2) is bonded to six equivalent O(1) atoms to form FeO6 octahedra that share corners with six equivalent Mg(1)O6 octahedra and edges with six equivalent Fe(1)O6 octahedra. The corner-sharing octahedral tilt angles are 3°. Co(1) is bonded in a distorted rectangular see-saw-like geometry to one O(2) and three equivalent O(1) atoms. There are two inequivalent O sites. In the first O site, O(1) is bonded to one Mg(1), one Fe(2), two equivalent Fe(1), and one Co(1) atom to form OMgFe3Co square pyramids that share corners with six equivalent O(1)MgFe3Co square pyramids, corners with three equivalent O(2)Fe3Co tetrahedra, edges with six equivalent O(1)MgFe3Co square pyramids, and  an edgeedge with one O(2)Fe3Co tetrahedra. In the second O site, O(2) is bonded to three equivalent Fe(1) and one Co(1) atom to form distorted OFe3Co tetrahedra that share corners with nine equivalent O(1)MgFe3Co square pyramids, corners with three equivalent O(2)Fe3Co tetrahedra, and edges with three equivalent O(1)MgFe3Co square pyramids.
MgFe4(CoO4)2 crystallizes in the trigonal R-3m space group. Mg(1) is bonded to six equivalent O(1) atoms to form MgO6 octahedra that share corners with six equivalent Fe(2)O6 octahedra and edges with six equivalent Fe(1)O6 octahedra. The corner-sharing octahedral tilt angles are 3°. All Mg(1)-O(1) bond lengths are 2.11 Å. There are two inequivalent Fe sites. In the first Fe site, Fe(1) is bonded to two equivalent O(2) and four equivalent O(1) atoms to form FeO6 octahedra that share edges with two equivalent Mg(1)O6 octahedra, edges with two equivalent Fe(2)O6 octahedra, and edges with four equivalent Fe(1)O6 octahedra. Both Fe(1)-O(2) bond lengths are 2.00 Å. All Fe(1)-O(1) bond lengths are 2.13 Å. In the second Fe site, Fe(2) is bonded to six equivalent O(1) atoms to form FeO6 octahedra that share corners with six equivalent Mg(1)O6 octahedra and edges with six equivalent Fe(1)O6 octahedra. The corner-sharing octahedral tilt angles are 3°. All Fe(2)-O(1) bond lengths are 2.24 Å. Co(1) is bonded in a distorted rectangular see-saw-like geometry to one O(2) and three equivalent O(1) atoms. The Co(1)-O(2) bond length is 1.87 Å. All Co(1)-O(1) bond lengths are 2.09 Å. There are two inequivalent O sites. In the first O site, O(1) is bonded to one Mg(1), one Fe(2), two equivalent Fe(1), and one Co(1) atom to form OMgFe3Co square pyramids that share corners with six equivalent O(1)MgFe3Co square pyramids, corners with three equivalent O(2)Fe3Co tetrahedra, edges with six equivalent O(1)MgFe3Co square pyramids, and  an edgeedge with one O(2)Fe3Co tetrahedra. In the second O site, O(2) is bonded to three equivalent Fe(1) and one Co(1) atom to form distorted OFe3Co tetrahedra that share corners with nine equivalent O(1)MgFe3Co square pyramids, corners with three equivalent O(2)Fe3Co tetrahedra, and edges with three equivalent O(1)MgFe3Co square pyramids.