Mg(FeO2)4 crystallizes in the monoclinic Pm space group. Mg(1) is bonded in a 6-coordinate geometry to one O(1), one O(6), two equivalent O(4), and two equivalent O(8) atoms. There are four inequivalent Fe sites. In the first Fe site, Fe(1) is bonded to one O(2), one O(5), two equivalent O(3), and two equivalent O(7) atoms to form a mixture of corner and edge-sharing FeO6 octahedra. The corner-sharing octahedral tilt angles are 50°. In the second Fe site, Fe(2) is bonded to one O(1), one O(6), two equivalent O(4), and two equivalent O(8) atoms to form a mixture of distorted corner and edge-sharing FeO6 octahedra. The corner-sharing octahedral tilt angles range from 47-56°. In the third Fe site, Fe(3) is bonded to one O(4), one O(7), two equivalent O(1), and two equivalent O(5) atoms to form a mixture of corner and edge-sharing FeO6 octahedra. The corner-sharing octahedral tilt angles range from 47-56°. In the fourth Fe site, Fe(4) is bonded to one O(3), one O(8), two equivalent O(2), and two equivalent O(6) atoms to form a mixture of corner and edge-sharing FeO6 octahedra. The corner-sharing octahedral tilt angles are 50°. There are eight inequivalent O sites. In the first O site, O(1) is bonded to one Mg(1), one Fe(2), and two equivalent Fe(3) atoms to form distorted OMgFe3 trigonal pyramids that share corners with two equivalent O(4)Mg2Fe3 trigonal bipyramids, corners with two equivalent O(1)MgFe3 trigonal pyramids, corners with two equivalent O(6)MgFe3 trigonal pyramids, edges with two equivalent O(4)Mg2Fe3 trigonal bipyramids, and edges with two equivalent O(8)Mg2Fe3 trigonal bipyramids. In the second O site, O(2) is bonded in a distorted trigonal planar geometry to one Fe(1) and two equivalent Fe(4) atoms. In the third O site, O(3) is bonded in a distorted trigonal planar geometry to one Fe(4) and two equivalent Fe(1) atoms. In the fourth O site, O(4) is bonded to two equivalent Mg(1), one Fe(3), and two equivalent Fe(2) atoms to form distorted OMg2Fe3 trigonal bipyramids that share corners with four equivalent O(8)Mg2Fe3 trigonal bipyramids, corners with two equivalent O(1)MgFe3 trigonal pyramids, edges with two equivalent O(4)Mg2Fe3 trigonal bipyramids, edges with two equivalent O(8)Mg2Fe3 trigonal bipyramids, edges with two equivalent O(1)MgFe3 trigonal pyramids, and edges with two equivalent O(6)MgFe3 trigonal pyramids. In the fifth O site, O(5) is bonded in a distorted trigonal non-coplanar geometry to one Fe(1) and two equivalent Fe(3) atoms. In the sixth O site, O(6) is bonded to one Mg(1), one Fe(2), and two equivalent Fe(4) atoms to form distorted OMgFe3 trigonal pyramids that share corners with two equivalent O(8)Mg2Fe3 trigonal bipyramids, corners with two equivalent O(1)MgFe3 trigonal pyramids, corners with two equivalent O(6)MgFe3 trigonal pyramids, edges with two equivalent O(4)Mg2Fe3 trigonal bipyramids, and edges with two equivalent O(8)Mg2Fe3 trigonal bipyramids. In the seventh O site, O(7) is bonded in a distorted trigonal non-coplanar geometry to one Fe(3) and two equivalent Fe(1) atoms. In the eighth O site, O(8) is bonded to two equivalent Mg(1), one Fe(4), and two equivalent Fe(2) atoms to form distorted OMg2Fe3 trigonal bipyramids that share corners with four equivalent O(4)Mg2Fe3 trigonal bipyramids, corners with two equivalent O(6)MgFe3 trigonal pyramids, edges with two equivalent O(4)Mg2Fe3 trigonal bipyramids, edges with two equivalent O(8)Mg2Fe3 trigonal bipyramids, edges with two equivalent O(1)MgFe3 trigonal pyramids, and edges with two equivalent O(6)MgFe3 trigonal pyramids.
Mg(FeO2)4 crystallizes in the monoclinic Pm space group. Mg(1) is bonded in a 6-coordinate geometry to one O(1), one O(6), two equivalent O(4), and two equivalent O(8) atoms. The Mg(1)-O(1) bond length is 2.17 Å. The Mg(1)-O(6) bond length is 1.98 Å. Both Mg(1)-O(4) bond lengths are 2.29 Å. Both Mg(1)-O(8) bond lengths are 2.06 Å. There are four inequivalent Fe sites. In the first Fe site, Fe(1) is bonded to one O(2), one O(5), two equivalent O(3), and two equivalent O(7) atoms to form a mixture of corner and edge-sharing FeO6 octahedra. The corner-sharing octahedral tilt angles are 50°. The Fe(1)-O(2) bond length is 2.03 Å. The Fe(1)-O(5) bond length is 2.09 Å. Both Fe(1)-O(3) bond lengths are 1.95 Å. Both Fe(1)-O(7) bond lengths are 1.94 Å. In the second Fe site, Fe(2) is bonded to one O(1), one O(6), two equivalent O(4), and two equivalent O(8) atoms to form a mixture of distorted corner and edge-sharing FeO6 octahedra. The corner-sharing octahedral tilt angles range from 47-56°. The Fe(2)-O(1) bond length is 1.96 Å. The Fe(2)-O(6) bond length is 2.06 Å. Both Fe(2)-O(4) bond lengths are 2.03 Å. Both Fe(2)-O(8) bond lengths are 2.15 Å. In the third Fe site, Fe(3) is bonded to one O(4), one O(7), two equivalent O(1), and two equivalent O(5) atoms to form a mixture of corner and edge-sharing FeO6 octahedra. The corner-sharing octahedral tilt angles range from 47-56°. The Fe(3)-O(4) bond length is 2.13 Å. The Fe(3)-O(7) bond length is 2.05 Å. Both Fe(3)-O(1) bond lengths are 2.03 Å. Both Fe(3)-O(5) bond lengths are 1.94 Å. In the fourth Fe site, Fe(4) is bonded to one O(3), one O(8), two equivalent O(2), and two equivalent O(6) atoms to form a mixture of corner and edge-sharing FeO6 octahedra. The corner-sharing octahedral tilt angles are 50°. The Fe(4)-O(3) bond length is 2.02 Å. The Fe(4)-O(8) bond length is 2.13 Å. Both Fe(4)-O(2) bond lengths are 1.95 Å. Both Fe(4)-O(6) bond lengths are 2.02 Å. There are eight inequivalent O sites. In the first O site, O(1) is bonded to one Mg(1), one Fe(2), and two equivalent Fe(3) atoms to form distorted OMgFe3 trigonal pyramids that share corners with two equivalent O(4)Mg2Fe3 trigonal bipyramids, corners with two equivalent O(1)MgFe3 trigonal pyramids, corners with two equivalent O(6)MgFe3 trigonal pyramids, edges with two equivalent O(4)Mg2Fe3 trigonal bipyramids, and edges with two equivalent O(8)Mg2Fe3 trigonal bipyramids. In the second O site, O(2) is bonded in a distorted trigonal planar geometry to one Fe(1) and two equivalent Fe(4) atoms. In the third O site, O(3) is bonded in a distorted trigonal planar geometry to one Fe(4) and two equivalent Fe(1) atoms. In the fourth O site, O(4) is bonded to two equivalent Mg(1), one Fe(3), and two equivalent Fe(2) atoms to form distorted OMg2Fe3 trigonal bipyramids that share corners with four equivalent O(8)Mg2Fe3 trigonal bipyramids, corners with two equivalent O(1)MgFe3 trigonal pyramids, edges with two equivalent O(4)Mg2Fe3 trigonal bipyramids, edges with two equivalent O(8)Mg2Fe3 trigonal bipyramids, edges with two equivalent O(1)MgFe3 trigonal pyramids, and edges with two equivalent O(6)MgFe3 trigonal pyramids. In the fifth O site, O(5) is bonded in a distorted trigonal non-coplanar geometry to one Fe(1) and two equivalent Fe(3) atoms. In the sixth O site, O(6) is bonded to one Mg(1), one Fe(2), and two equivalent Fe(4) atoms to form distorted OMgFe3 trigonal pyramids that share corners with two equivalent O(8)Mg2Fe3 trigonal bipyramids, corners with two equivalent O(1)MgFe3 trigonal pyramids, corners with two equivalent O(6)MgFe3 trigonal pyramids, edges with two equivalent O(4)Mg2Fe3 trigonal bipyramids, and edges with two equivalent O(8)Mg2Fe3 trigonal bipyramids. In the seventh O site, O(7) is bonded in a distorted trigonal non-coplanar geometry to one Fe(3) and two equivalent Fe(1) atoms. In the eighth O site, O(8) is bonded to two equivalent Mg(1), one Fe(4), and two equivalent Fe(2) atoms to form distorted OMg2Fe3 trigonal bipyramids that share corners with four equivalent O(4)Mg2Fe3 trigonal bipyramids, corners with two equivalent O(6)MgFe3 trigonal pyramids, edges with two equivalent O(4)Mg2Fe3 trigonal bipyramids, edges with two equivalent O(8)Mg2Fe3 trigonal bipyramids, edges with two equivalent O(1)MgFe3 trigonal pyramids, and edges with two equivalent O(6)MgFe3 trigonal pyramids.