MgFe4(CuO4)3 crystallizes in the trigonal R-3 space group. Mg(1) is bonded to six equivalent O(1) and six equivalent O(2) atoms to form MgO12 cuboctahedra that share faces with two equivalent Fe(2)O6 octahedra and faces with six equivalent Fe(1)O6 octahedra. There are two inequivalent Fe sites. In the first Fe site, Fe(1) is bonded to two equivalent O(1) and four equivalent O(2) atoms to form FeO6 octahedra that share corners with two equivalent Fe(2)O6 octahedra, corners with four equivalent Fe(1)O6 octahedra, and faces with two equivalent Mg(1)O12 cuboctahedra. The corner-sharing octahedral tilt angles range from 44-45°. 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 Fe(1)O6 octahedra and faces with two equivalent Mg(1)O12 cuboctahedra. The corner-sharing octahedral tilt angles are 45°. Cu(1) is bonded in a square co-planar geometry to two equivalent O(1) and two equivalent O(2) atoms. There are two inequivalent O sites. In the first O site, O(1) is bonded in a 4-coordinate geometry to one Mg(1), one Fe(1), one Fe(2), and one Cu(1) atom. In the second O site, O(2) is bonded in a 3-coordinate geometry to one Mg(1), two equivalent Fe(1), and one Cu(1) atom.
MgFe4(CuO4)3 crystallizes in the trigonal R-3 space group. Mg(1) is bonded to six equivalent O(1) and six equivalent O(2) atoms to form MgO12 cuboctahedra that share faces with two equivalent Fe(2)O6 octahedra and faces with six equivalent Fe(1)O6 octahedra. All Mg(1)-O(1) bond lengths are 2.60 Å. All Mg(1)-O(2) bond lengths are 2.61 Å. There are two inequivalent Fe sites. In the first Fe site, Fe(1) is bonded to two equivalent O(1) and four equivalent O(2) atoms to form FeO6 octahedra that share corners with two equivalent Fe(2)O6 octahedra, corners with four equivalent Fe(1)O6 octahedra, and faces with two equivalent Mg(1)O12 cuboctahedra. The corner-sharing octahedral tilt angles range from 44-45°. Both Fe(1)-O(1) bond lengths are 1.99 Å. There are two shorter (1.99 Å) and two longer (2.01 Å) Fe(1)-O(2) bond lengths. 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 Fe(1)O6 octahedra and faces with two equivalent Mg(1)O12 cuboctahedra. The corner-sharing octahedral tilt angles are 45°. All Fe(2)-O(1) bond lengths are 2.01 Å. Cu(1) is bonded in a square co-planar geometry to two equivalent O(1) and two equivalent O(2) atoms. Both Cu(1)-O(1) bond lengths are 1.87 Å. Both Cu(1)-O(2) bond lengths are 1.87 Å. There are two inequivalent O sites. In the first O site, O(1) is bonded in a 4-coordinate geometry to one Mg(1), one Fe(1), one Fe(2), and one Cu(1) atom. In the second O site, O(2) is bonded in a 3-coordinate geometry to one Mg(1), two equivalent Fe(1), and one Cu(1) atom.