MgFe4(CuO4)2 crystallizes in the triclinic P1 space group. Mg(1) is bonded to one O(2), one O(4), one O(7), and one O(8) atom to form MgO4 tetrahedra that share corners with two equivalent Cu(1)O5 square pyramids, corners with two equivalent Cu(2)O5 square pyramids, corners with two equivalent Fe(1)O4 tetrahedra, and  an edgeedge with one Fe(2)O4 tetrahedra. There are four inequivalent Fe sites. In the first Fe site, Fe(1) is bonded to one O(5), one O(6), one O(7), and one O(8) atom to form FeO4 tetrahedra that share corners with two equivalent Cu(1)O5 square pyramids, corners with two equivalent Cu(2)O5 square pyramids, and corners with two equivalent Mg(1)O4 tetrahedra. In the second Fe site, Fe(2) is bonded to one O(1), one O(2), one O(3), and one O(4) atom to form distorted FeO4 tetrahedra that share corners with three equivalent Cu(1)O5 square pyramids, corners with three equivalent Cu(2)O5 square pyramids, and  an edgeedge with one Mg(1)O4 tetrahedra. In the third Fe site, Fe(3) is bonded in a 5-coordinate geometry to one O(1), one O(3), one O(6), one O(7), and one O(8) atom. In the fourth Fe site, Fe(4) is bonded in a 5-coordinate geometry to one O(1), one O(3), one O(5), one O(7), and one O(8) atom. There are two inequivalent Cu sites. In the first Cu site, Cu(1) is bonded to one O(1), one O(2), one O(4), one O(5), and one O(6) atom to form distorted CuO5 square pyramids that share corners with two equivalent Mg(1)O4 tetrahedra, corners with two equivalent Fe(1)O4 tetrahedra, corners with three equivalent Fe(2)O4 tetrahedra, and edges with two equivalent Cu(2)O5 square pyramids. In the second Cu site, Cu(2) is bonded to one O(2), one O(3), one O(4), one O(5), and one O(6) atom to form distorted CuO5 square pyramids that share corners with two equivalent Mg(1)O4 tetrahedra, corners with two equivalent Fe(1)O4 tetrahedra, corners with three equivalent Fe(2)O4 tetrahedra, and edges with two equivalent Cu(1)O5 square pyramids. There are eight inequivalent O sites. In the first O site, O(1) is bonded to one Fe(2), one Fe(3), one Fe(4), and one Cu(1) atom to form OFe3Cu tetrahedra that share  a cornercorner with one O(3)Fe3Cu tetrahedra, corners with two equivalent O(2)MgFeCu2 tetrahedra, corners with two equivalent O(4)MgFeCu2 tetrahedra, corners with two equivalent O(7)MgFe3 trigonal pyramids, corners with two equivalent O(8)MgFe3 trigonal pyramids, and  an edgeedge with one O(3)Fe3Cu tetrahedra. In the second O site, O(2) is bonded to one Mg(1), one Fe(2), one Cu(1), and one Cu(2) atom to form distorted OMgFeCu2 tetrahedra that share corners with two equivalent O(1)Fe3Cu tetrahedra, corners with two equivalent O(3)Fe3Cu tetrahedra,  a cornercorner with one O(7)MgFe3 trigonal pyramid,  a cornercorner with one O(8)MgFe3 trigonal pyramid, and edges with two equivalent O(4)MgFeCu2 tetrahedra. In the third O site, O(3) is bonded to one Fe(2), one Fe(3), one Fe(4), and one Cu(2) atom to form OFe3Cu tetrahedra that share  a cornercorner with one O(1)Fe3Cu tetrahedra, corners with two equivalent O(2)MgFeCu2 tetrahedra, corners with two equivalent O(4)MgFeCu2 tetrahedra, corners with two equivalent O(7)MgFe3 trigonal pyramids, corners with two equivalent O(8)MgFe3 trigonal pyramids, and  an edgeedge with one O(1)Fe3Cu tetrahedra. In the fourth O site, O(4) is bonded to one Mg(1), one Fe(2), one Cu(1), and one Cu(2) atom to form distorted OMgFeCu2 tetrahedra that share corners with two equivalent O(1)Fe3Cu tetrahedra, corners with two equivalent O(3)Fe3Cu tetrahedra,  a cornercorner with one O(7)MgFe3 trigonal pyramid,  a cornercorner with one O(8)MgFe3 trigonal pyramid, and edges with two equivalent O(2)MgFeCu2 tetrahedra. In the fifth O site, O(5) is bonded in a rectangular see-saw-like geometry to one Fe(1), one Fe(4), one Cu(1), and one Cu(2) atom. In the sixth O site, O(6) is bonded in a rectangular see-saw-like geometry to one Fe(1), one Fe(3), one Cu(1), and one Cu(2) atom. In the seventh O site, O(7) is bonded to one Mg(1), one Fe(1), one Fe(3), and one Fe(4) atom to form distorted OMgFe3 trigonal pyramids that share  a cornercorner with one O(2)MgFeCu2 tetrahedra,  a cornercorner with one O(4)MgFeCu2 tetrahedra, corners with two equivalent O(1)Fe3Cu tetrahedra, corners with two equivalent O(3)Fe3Cu tetrahedra,  a cornercorner with one O(8)MgFe3 trigonal pyramid, and  a faceface with one O(8)MgFe3 trigonal pyramid. In the eighth O site, O(8) is bonded to one Mg(1), one Fe(1), one Fe(3), and one Fe(4) atom to form distorted OMgFe3 trigonal pyramids that share  a cornercorner with one O(2)MgFeCu2 tetrahedra,  a cornercorner with one O(4)MgFeCu2 tetrahedra, corners with two equivalent O(1)Fe3Cu tetrahedra, corners with two equivalent O(3)Fe3Cu tetrahedra,  a cornercorner with one O(7)MgFe3 trigonal pyramid, and  a faceface with one O(7)MgFe3 trigonal pyramid.
MgFe4(CuO4)2 crystallizes in the triclinic P1 space group. Mg(1) is bonded to one O(2), one O(4), one O(7), and one O(8) atom to form MgO4 tetrahedra that share corners with two equivalent Cu(1)O5 square pyramids, corners with two equivalent Cu(2)O5 square pyramids, corners with two equivalent Fe(1)O4 tetrahedra, and  an edgeedge with one Fe(2)O4 tetrahedra. The Mg(1)-O(2) bond length is 1.93 Å. The Mg(1)-O(4) bond length is 1.94 Å. The Mg(1)-O(7) bond length is 1.96 Å. The Mg(1)-O(8) bond length is 1.96 Å. There are four inequivalent Fe sites. In the first Fe site, Fe(1) is bonded to one O(5), one O(6), one O(7), and one O(8) atom to form FeO4 tetrahedra that share corners with two equivalent Cu(1)O5 square pyramids, corners with two equivalent Cu(2)O5 square pyramids, and corners with two equivalent Mg(1)O4 tetrahedra. The Fe(1)-O(5) bond length is 2.02 Å. The Fe(1)-O(6) bond length is 1.95 Å. The Fe(1)-O(7) bond length is 1.92 Å. The Fe(1)-O(8) bond length is 1.92 Å. In the second Fe site, Fe(2) is bonded to one O(1), one O(2), one O(3), and one O(4) atom to form distorted FeO4 tetrahedra that share corners with three equivalent Cu(1)O5 square pyramids, corners with three equivalent Cu(2)O5 square pyramids, and  an edgeedge with one Mg(1)O4 tetrahedra. The Fe(2)-O(1) bond length is 1.91 Å. The Fe(2)-O(2) bond length is 2.17 Å. The Fe(2)-O(3) bond length is 1.91 Å. The Fe(2)-O(4) bond length is 2.15 Å. In the third Fe site, Fe(3) is bonded in a 5-coordinate geometry to one O(1), one O(3), one O(6), one O(7), and one O(8) atom. The Fe(3)-O(1) bond length is 2.04 Å. The Fe(3)-O(3) bond length is 2.04 Å. The Fe(3)-O(6) bond length is 2.05 Å. The Fe(3)-O(7) bond length is 2.24 Å. The Fe(3)-O(8) bond length is 2.25 Å. In the fourth Fe site, Fe(4) is bonded in a 5-coordinate geometry to one O(1), one O(3), one O(5), one O(7), and one O(8) atom. The Fe(4)-O(1) bond length is 1.92 Å. The Fe(4)-O(3) bond length is 1.92 Å. The Fe(4)-O(5) bond length is 2.03 Å. The Fe(4)-O(7) bond length is 2.16 Å. The Fe(4)-O(8) bond length is 2.18 Å. There are two inequivalent Cu sites. In the first Cu site, Cu(1) is bonded to one O(1), one O(2), one O(4), one O(5), and one O(6) atom to form distorted CuO5 square pyramids that share corners with two equivalent Mg(1)O4 tetrahedra, corners with two equivalent Fe(1)O4 tetrahedra, corners with three equivalent Fe(2)O4 tetrahedra, and edges with two equivalent Cu(2)O5 square pyramids. The Cu(1)-O(1) bond length is 2.50 Å. The Cu(1)-O(2) bond length is 1.97 Å. The Cu(1)-O(4) bond length is 2.00 Å. The Cu(1)-O(5) bond length is 2.10 Å. The Cu(1)-O(6) bond length is 2.04 Å. In the second Cu site, Cu(2) is bonded to one O(2), one O(3), one O(4), one O(5), and one O(6) atom to form distorted CuO5 square pyramids that share corners with two equivalent Mg(1)O4 tetrahedra, corners with two equivalent Fe(1)O4 tetrahedra, corners with three equivalent Fe(2)O4 tetrahedra, and edges with two equivalent Cu(1)O5 square pyramids. The Cu(2)-O(2) bond length is 1.97 Å. The Cu(2)-O(3) bond length is 2.49 Å. The Cu(2)-O(4) bond length is 2.00 Å. The Cu(2)-O(5) bond length is 2.10 Å. The Cu(2)-O(6) bond length is 2.04 Å. There are eight inequivalent O sites. In the first O site, O(1) is bonded to one Fe(2), one Fe(3), one Fe(4), and one Cu(1) atom to form OFe3Cu tetrahedra that share  a cornercorner with one O(3)Fe3Cu tetrahedra, corners with two equivalent O(2)MgFeCu2 tetrahedra, corners with two equivalent O(4)MgFeCu2 tetrahedra, corners with two equivalent O(7)MgFe3 trigonal pyramids, corners with two equivalent O(8)MgFe3 trigonal pyramids, and  an edgeedge with one O(3)Fe3Cu tetrahedra. In the second O site, O(2) is bonded to one Mg(1), one Fe(2), one Cu(1), and one Cu(2) atom to form distorted OMgFeCu2 tetrahedra that share corners with two equivalent O(1)Fe3Cu tetrahedra, corners with two equivalent O(3)Fe3Cu tetrahedra,  a cornercorner with one O(7)MgFe3 trigonal pyramid,  a cornercorner with one O(8)MgFe3 trigonal pyramid, and edges with two equivalent O(4)MgFeCu2 tetrahedra. In the third O site, O(3) is bonded to one Fe(2), one Fe(3), one Fe(4), and one Cu(2) atom to form OFe3Cu tetrahedra that share  a cornercorner with one O(1)Fe3Cu tetrahedra, corners with two equivalent O(2)MgFeCu2 tetrahedra, corners with two equivalent O(4)MgFeCu2 tetrahedra, corners with two equivalent O(7)MgFe3 trigonal pyramids, corners with two equivalent O(8)MgFe3 trigonal pyramids, and  an edgeedge with one O(1)Fe3Cu tetrahedra. In the fourth O site, O(4) is bonded to one Mg(1), one Fe(2), one Cu(1), and one Cu(2) atom to form distorted OMgFeCu2 tetrahedra that share corners with two equivalent O(1)Fe3Cu tetrahedra, corners with two equivalent O(3)Fe3Cu tetrahedra,  a cornercorner with one O(7)MgFe3 trigonal pyramid,  a cornercorner with one O(8)MgFe3 trigonal pyramid, and edges with two equivalent O(2)MgFeCu2 tetrahedra. In the fifth O site, O(5) is bonded in a rectangular see-saw-like geometry to one Fe(1), one Fe(4), one Cu(1), and one Cu(2) atom. In the sixth O site, O(6) is bonded in a rectangular see-saw-like geometry to one Fe(1), one Fe(3), one Cu(1), and one Cu(2) atom. In the seventh O site, O(7) is bonded to one Mg(1), one Fe(1), one Fe(3), and one Fe(4) atom to form distorted OMgFe3 trigonal pyramids that share  a cornercorner with one O(2)MgFeCu2 tetrahedra,  a cornercorner with one O(4)MgFeCu2 tetrahedra, corners with two equivalent O(1)Fe3Cu tetrahedra, corners with two equivalent O(3)Fe3Cu tetrahedra,  a cornercorner with one O(8)MgFe3 trigonal pyramid, and  a faceface with one O(8)MgFe3 trigonal pyramid. In the eighth O site, O(8) is bonded to one Mg(1), one Fe(1), one Fe(3), and one Fe(4) atom to form distorted OMgFe3 trigonal pyramids that share  a cornercorner with one O(2)MgFeCu2 tetrahedra,  a cornercorner with one O(4)MgFeCu2 tetrahedra, corners with two equivalent O(1)Fe3Cu tetrahedra, corners with two equivalent O(3)Fe3Cu tetrahedra,  a cornercorner with one O(7)MgFe3 trigonal pyramid, and  a faceface with one O(7)MgFe3 trigonal pyramid.