Na4Mg(FeO2)4 crystallizes in the triclinic P1 space group. There are four inequivalent Na sites. In the first Na site, Na(1) is bonded to one O(1), one O(2), one O(5), and one O(8) atom to form NaO4 tetrahedra that share corners with two equivalent Na(2)O4 tetrahedra, corners with two equivalent Fe(1)O4 tetrahedra, corners with two equivalent Fe(2)O4 tetrahedra, corners with two equivalent Fe(3)O4 tetrahedra, corners with two equivalent Fe(4)O4 tetrahedra, and corners with two equivalent Na(4)O4 trigonal pyramids. In the second Na site, Na(2) is bonded to one O(1), one O(2), one O(6), and one O(7) atom to form distorted NaO4 tetrahedra that share corners with two equivalent Na(1)O4 tetrahedra, corners with two equivalent Fe(1)O4 tetrahedra, corners with two equivalent Fe(2)O4 tetrahedra, corners with two equivalent Fe(3)O4 tetrahedra, corners with two equivalent Fe(4)O4 tetrahedra, and  an edgeedge with one Mg(1)O4 trigonal pyramid. In the third Na site, Na(3) is bonded in a 4-coordinate geometry to one O(3), one O(4), one O(7), and one O(8) atom. In the fourth Na site, Na(4) is bonded to one O(3), one O(4), one O(5), and one O(8) atom to form distorted NaO4 trigonal pyramids that share corners with two equivalent Na(1)O4 tetrahedra, corners with two equivalent Fe(2)O4 tetrahedra, corners with two equivalent Fe(3)O4 tetrahedra, corners with two equivalent Mg(1)O4 trigonal pyramids,  an edgeedge with one Fe(1)O4 tetrahedra, and  an edgeedge with one Fe(4)O4 tetrahedra. Mg(1) is bonded to one O(3), one O(4), one O(6), and one O(7) atom to form distorted MgO4 trigonal pyramids that share corners with two equivalent Fe(1)O4 tetrahedra, corners with two equivalent Fe(3)O4 tetrahedra, corners with two equivalent Na(4)O4 trigonal pyramids,  an edgeedge with one Na(2)O4 tetrahedra,  an edgeedge with one Fe(2)O4 tetrahedra, and  an edgeedge with one Fe(4)O4 tetrahedra. There are four inequivalent Fe sites. In the first Fe site, Fe(1) is bonded to one O(1), one O(4), one O(5), and one O(6) atom to form FeO4 tetrahedra that share corners with two equivalent Na(1)O4 tetrahedra, corners with two equivalent Na(2)O4 tetrahedra, corners with two equivalent Fe(2)O4 tetrahedra, corners with two equivalent Fe(4)O4 tetrahedra, corners with two equivalent Mg(1)O4 trigonal pyramids, and  an edgeedge with one Na(4)O4 trigonal pyramid. In the second Fe site, Fe(2) is bonded to one O(2), one O(3), one O(5), and one O(6) atom to form distorted FeO4 tetrahedra that share corners with two equivalent Na(1)O4 tetrahedra, corners with two equivalent Na(2)O4 tetrahedra, corners with two equivalent Fe(1)O4 tetrahedra, corners with two equivalent Fe(3)O4 tetrahedra, corners with two equivalent Na(4)O4 trigonal pyramids, and  an edgeedge with one Mg(1)O4 trigonal pyramid. In the third Fe site, Fe(3) is bonded to one O(2), one O(3), one O(7), and one O(8) atom to form FeO4 tetrahedra that share corners with two equivalent Na(1)O4 tetrahedra, corners with two equivalent Na(2)O4 tetrahedra, corners with two equivalent Fe(2)O4 tetrahedra, corners with two equivalent Fe(4)O4 tetrahedra, corners with two equivalent Na(4)O4 trigonal pyramids, and corners with two equivalent Mg(1)O4 trigonal pyramids. In the fourth Fe site, Fe(4) is bonded to one O(1), one O(4), one O(7), and one O(8) atom to form distorted FeO4 tetrahedra that share corners with two equivalent Na(1)O4 tetrahedra, corners with two equivalent Na(2)O4 tetrahedra, corners with two equivalent Fe(1)O4 tetrahedra, corners with two equivalent Fe(3)O4 tetrahedra,  an edgeedge with one Na(4)O4 trigonal pyramid, and  an edgeedge with one Mg(1)O4 trigonal pyramid. There are eight inequivalent O sites. In the first O site, O(1) is bonded to one Na(1), one Na(2), one Fe(1), and one Fe(4) atom to form corner-sharing ONa2Fe2 tetrahedra. In the second O site, O(2) is bonded to one Na(1), one Na(2), one Fe(2), and one Fe(3) atom to form distorted ONa2Fe2 tetrahedra that share corners with two equivalent O(1)Na2Fe2 tetrahedra, corners with two equivalent O(3)Na2MgFe2 trigonal bipyramids, and corners with two equivalent O(5)Na2Fe2 trigonal pyramids. In the third O site, O(3) is bonded to one Na(3), one Na(4), one Mg(1), one Fe(2), and one Fe(3) atom to form distorted corner-sharing ONa2MgFe2 trigonal bipyramids. In the fourth O site, O(4) is bonded in a 5-coordinate geometry to one Na(3), one Na(4), one Mg(1), one Fe(1), and one Fe(4) atom. In the fifth O site, O(5) is bonded to one Na(1), one Na(4), one Fe(1), and one Fe(2) atom to form ONa2Fe2 trigonal pyramids that share corners with two equivalent O(1)Na2Fe2 tetrahedra, corners with two equivalent O(2)Na2Fe2 tetrahedra, and corners with two equivalent O(3)Na2MgFe2 trigonal bipyramids. In the sixth O site, O(6) is bonded in a 4-coordinate geometry to one Na(2), one Mg(1), one Fe(1), and one Fe(2) atom. In the seventh O site, O(7) is bonded in a 5-coordinate geometry to one Na(2), one Na(3), one Mg(1), one Fe(3), and one Fe(4) atom. In the eighth O site, O(8) is bonded in a 5-coordinate geometry to one Na(1), one Na(3), one Na(4), one Fe(3), and one Fe(4) atom.
Na4Mg(FeO2)4 crystallizes in the triclinic P1 space group. There are four inequivalent Na sites. In the first Na site, Na(1) is bonded to one O(1), one O(2), one O(5), and one O(8) atom to form NaO4 tetrahedra that share corners with two equivalent Na(2)O4 tetrahedra, corners with two equivalent Fe(1)O4 tetrahedra, corners with two equivalent Fe(2)O4 tetrahedra, corners with two equivalent Fe(3)O4 tetrahedra, corners with two equivalent Fe(4)O4 tetrahedra, and corners with two equivalent Na(4)O4 trigonal pyramids. The Na(1)-O(1) bond length is 2.32 Å. The Na(1)-O(2) bond length is 2.33 Å. The Na(1)-O(5) bond length is 2.32 Å. The Na(1)-O(8) bond length is 2.33 Å. In the second Na site, Na(2) is bonded to one O(1), one O(2), one O(6), and one O(7) atom to form distorted NaO4 tetrahedra that share corners with two equivalent Na(1)O4 tetrahedra, corners with two equivalent Fe(1)O4 tetrahedra, corners with two equivalent Fe(2)O4 tetrahedra, corners with two equivalent Fe(3)O4 tetrahedra, corners with two equivalent Fe(4)O4 tetrahedra, and  an edgeedge with one Mg(1)O4 trigonal pyramid. The Na(2)-O(1) bond length is 2.25 Å. The Na(2)-O(2) bond length is 2.37 Å. The Na(2)-O(6) bond length is 2.30 Å. The Na(2)-O(7) bond length is 2.38 Å. In the third Na site, Na(3) is bonded in a 4-coordinate geometry to one O(3), one O(4), one O(7), and one O(8) atom. The Na(3)-O(3) bond length is 2.42 Å. The Na(3)-O(4) bond length is 2.52 Å. The Na(3)-O(7) bond length is 2.52 Å. The Na(3)-O(8) bond length is 2.70 Å. In the fourth Na site, Na(4) is bonded to one O(3), one O(4), one O(5), and one O(8) atom to form distorted NaO4 trigonal pyramids that share corners with two equivalent Na(1)O4 tetrahedra, corners with two equivalent Fe(2)O4 tetrahedra, corners with two equivalent Fe(3)O4 tetrahedra, corners with two equivalent Mg(1)O4 trigonal pyramids,  an edgeedge with one Fe(1)O4 tetrahedra, and  an edgeedge with one Fe(4)O4 tetrahedra. The Na(4)-O(3) bond length is 2.28 Å. The Na(4)-O(4) bond length is 2.49 Å. The Na(4)-O(5) bond length is 2.23 Å. The Na(4)-O(8) bond length is 2.32 Å. Mg(1) is bonded to one O(3), one O(4), one O(6), and one O(7) atom to form distorted MgO4 trigonal pyramids that share corners with two equivalent Fe(1)O4 tetrahedra, corners with two equivalent Fe(3)O4 tetrahedra, corners with two equivalent Na(4)O4 trigonal pyramids,  an edgeedge with one Na(2)O4 tetrahedra,  an edgeedge with one Fe(2)O4 tetrahedra, and  an edgeedge with one Fe(4)O4 tetrahedra. The Mg(1)-O(3) bond length is 2.01 Å. The Mg(1)-O(4) bond length is 1.98 Å. The Mg(1)-O(6) bond length is 2.01 Å. The Mg(1)-O(7) bond length is 2.02 Å. There are four inequivalent Fe sites. In the first Fe site, Fe(1) is bonded to one O(1), one O(4), one O(5), and one O(6) atom to form FeO4 tetrahedra that share corners with two equivalent Na(1)O4 tetrahedra, corners with two equivalent Na(2)O4 tetrahedra, corners with two equivalent Fe(2)O4 tetrahedra, corners with two equivalent Fe(4)O4 tetrahedra, corners with two equivalent Mg(1)O4 trigonal pyramids, and  an edgeedge with one Na(4)O4 trigonal pyramid. The Fe(1)-O(1) bond length is 1.89 Å. The Fe(1)-O(4) bond length is 1.98 Å. The Fe(1)-O(5) bond length is 1.90 Å. The Fe(1)-O(6) bond length is 1.93 Å. In the second Fe site, Fe(2) is bonded to one O(2), one O(3), one O(5), and one O(6) atom to form distorted FeO4 tetrahedra that share corners with two equivalent Na(1)O4 tetrahedra, corners with two equivalent Na(2)O4 tetrahedra, corners with two equivalent Fe(1)O4 tetrahedra, corners with two equivalent Fe(3)O4 tetrahedra, corners with two equivalent Na(4)O4 trigonal pyramids, and  an edgeedge with one Mg(1)O4 trigonal pyramid. The Fe(2)-O(2) bond length is 1.98 Å. The Fe(2)-O(3) bond length is 2.18 Å. The Fe(2)-O(5) bond length is 1.93 Å. The Fe(2)-O(6) bond length is 2.24 Å. In the third Fe site, Fe(3) is bonded to one O(2), one O(3), one O(7), and one O(8) atom to form FeO4 tetrahedra that share corners with two equivalent Na(1)O4 tetrahedra, corners with two equivalent Na(2)O4 tetrahedra, corners with two equivalent Fe(2)O4 tetrahedra, corners with two equivalent Fe(4)O4 tetrahedra, corners with two equivalent Na(4)O4 trigonal pyramids, and corners with two equivalent Mg(1)O4 trigonal pyramids. The Fe(3)-O(2) bond length is 1.91 Å. The Fe(3)-O(3) bond length is 1.96 Å. The Fe(3)-O(7) bond length is 1.92 Å. The Fe(3)-O(8) bond length is 1.91 Å. In the fourth Fe site, Fe(4) is bonded to one O(1), one O(4), one O(7), and one O(8) atom to form distorted FeO4 tetrahedra that share corners with two equivalent Na(1)O4 tetrahedra, corners with two equivalent Na(2)O4 tetrahedra, corners with two equivalent Fe(1)O4 tetrahedra, corners with two equivalent Fe(3)O4 tetrahedra,  an edgeedge with one Na(4)O4 trigonal pyramid, and  an edgeedge with one Mg(1)O4 trigonal pyramid. The Fe(4)-O(1) bond length is 1.95 Å. The Fe(4)-O(4) bond length is 2.15 Å. The Fe(4)-O(7) bond length is 2.12 Å. The Fe(4)-O(8) bond length is 1.99 Å. There are eight inequivalent O sites. In the first O site, O(1) is bonded to one Na(1), one Na(2), one Fe(1), and one Fe(4) atom to form corner-sharing ONa2Fe2 tetrahedra. In the second O site, O(2) is bonded to one Na(1), one Na(2), one Fe(2), and one Fe(3) atom to form distorted ONa2Fe2 tetrahedra that share corners with two equivalent O(1)Na2Fe2 tetrahedra, corners with two equivalent O(3)Na2MgFe2 trigonal bipyramids, and corners with two equivalent O(5)Na2Fe2 trigonal pyramids. In the third O site, O(3) is bonded to one Na(3), one Na(4), one Mg(1), one Fe(2), and one Fe(3) atom to form distorted corner-sharing ONa2MgFe2 trigonal bipyramids. In the fourth O site, O(4) is bonded in a 5-coordinate geometry to one Na(3), one Na(4), one Mg(1), one Fe(1), and one Fe(4) atom. In the fifth O site, O(5) is bonded to one Na(1), one Na(4), one Fe(1), and one Fe(2) atom to form ONa2Fe2 trigonal pyramids that share corners with two equivalent O(1)Na2Fe2 tetrahedra, corners with two equivalent O(2)Na2Fe2 tetrahedra, and corners with two equivalent O(3)Na2MgFe2 trigonal bipyramids. In the sixth O site, O(6) is bonded in a 4-coordinate geometry to one Na(2), one Mg(1), one Fe(1), and one Fe(2) atom. In the seventh O site, O(7) is bonded in a 5-coordinate geometry to one Na(2), one Na(3), one Mg(1), one Fe(3), and one Fe(4) atom. In the eighth O site, O(8) is bonded in a 5-coordinate geometry to one Na(1), one Na(3), one Na(4), one Fe(3), and one Fe(4) atom.