Na4Mg(FeO3)2 crystallizes in the triclinic P1 space group. There are four inequivalent Na sites. In the first Na site, Na(1) is bonded in a 6-coordinate geometry to one O(1), one O(2), one O(3), one O(4), one O(5), and one O(6) atom. In the second Na site, Na(2) is bonded in a 5-coordinate geometry to one O(1), one O(3), one O(4), one O(5), and one O(6) atom. In the third Na site, Na(3) is bonded in a 4-coordinate geometry to one O(1), one O(2), one O(3), and one O(4) atom. In the fourth Na site, Na(4) is bonded in a 4-coordinate geometry to one O(1), one O(2), one O(4), one O(5), and one O(6) atom. Mg(1) is bonded to one O(2), one O(3), one O(5), and one O(6) atom to form MgO4 tetrahedra that share corners with two equivalent Fe(1)O4 tetrahedra and corners with three equivalent Fe(2)O5 trigonal bipyramids. There are two inequivalent Fe sites. In the first Fe site, Fe(1) is bonded to one O(1), one O(3), one O(4), and one O(6) atom to form distorted FeO4 tetrahedra that share corners with two equivalent Mg(1)O4 tetrahedra,  a cornercorner with one Fe(2)O5 trigonal bipyramid, and  an edgeedge with one Fe(2)O5 trigonal bipyramid. In the second Fe site, Fe(2) is bonded to one O(1), one O(2), one O(4), one O(5), and one O(6) atom to form distorted FeO5 trigonal bipyramids that share  a cornercorner with one Fe(1)O4 tetrahedra, corners with three equivalent Mg(1)O4 tetrahedra, and  an edgeedge with one Fe(1)O4 tetrahedra. There are six inequivalent O sites. In the first O site, O(1) is bonded in a 6-coordinate geometry to one Na(1), one Na(2), one Na(3), one Na(4), one Fe(1), and one Fe(2) atom. In the second O site, O(2) is bonded to one Na(1), one Na(3), one Na(4), one Mg(1), and one Fe(2) atom to form a mixture of distorted corner and edge-sharing ONa3MgFe trigonal bipyramids. In the third O site, O(3) is bonded in a 5-coordinate geometry to one Na(1), one Na(2), one Na(3), one Mg(1), and one Fe(1) atom. In the fourth O site, O(4) is bonded in a 6-coordinate geometry to one Na(1), one Na(2), one Na(3), one Na(4), one Fe(1), and one Fe(2) atom. In the fifth O site, O(5) is bonded to one Na(1), one Na(2), one Na(4), one Mg(1), and one Fe(2) atom to form a mixture of corner and edge-sharing ONa3MgFe trigonal bipyramids. In the sixth O site, O(6) is bonded in a 6-coordinate geometry to one Na(1), one Na(2), one Na(4), one Mg(1), one Fe(1), and one Fe(2) atom.
Na4Mg(FeO3)2 crystallizes in the triclinic P1 space group. There are four inequivalent Na sites. In the first Na site, Na(1) is bonded in a 6-coordinate geometry to one O(1), one O(2), one O(3), one O(4), one O(5), and one O(6) atom. The Na(1)-O(1) bond length is 2.64 Å. The Na(1)-O(2) bond length is 2.57 Å. The Na(1)-O(3) bond length is 2.41 Å. The Na(1)-O(4) bond length is 2.44 Å. The Na(1)-O(5) bond length is 2.34 Å. The Na(1)-O(6) bond length is 2.83 Å. In the second Na site, Na(2) is bonded in a 5-coordinate geometry to one O(1), one O(3), one O(4), one O(5), and one O(6) atom. The Na(2)-O(1) bond length is 2.24 Å. The Na(2)-O(3) bond length is 2.44 Å. The Na(2)-O(4) bond length is 2.66 Å. The Na(2)-O(5) bond length is 2.29 Å. The Na(2)-O(6) bond length is 2.66 Å. In the third Na site, Na(3) is bonded in a 4-coordinate geometry to one O(1), one O(2), one O(3), and one O(4) atom. The Na(3)-O(1) bond length is 2.41 Å. The Na(3)-O(2) bond length is 2.33 Å. The Na(3)-O(3) bond length is 2.25 Å. The Na(3)-O(4) bond length is 2.47 Å. In the fourth Na site, Na(4) is bonded in a 4-coordinate geometry to one O(1), one O(2), one O(4), one O(5), and one O(6) atom. The Na(4)-O(1) bond length is 2.96 Å. The Na(4)-O(2) bond length is 2.33 Å. The Na(4)-O(4) bond length is 2.31 Å. The Na(4)-O(5) bond length is 2.51 Å. The Na(4)-O(6) bond length is 2.58 Å. Mg(1) is bonded to one O(2), one O(3), one O(5), and one O(6) atom to form MgO4 tetrahedra that share corners with two equivalent Fe(1)O4 tetrahedra and corners with three equivalent Fe(2)O5 trigonal bipyramids. The Mg(1)-O(2) bond length is 1.99 Å. The Mg(1)-O(3) bond length is 1.94 Å. The Mg(1)-O(5) bond length is 1.96 Å. The Mg(1)-O(6) bond length is 2.06 Å. There are two inequivalent Fe sites. In the first Fe site, Fe(1) is bonded to one O(1), one O(3), one O(4), and one O(6) atom to form distorted FeO4 tetrahedra that share corners with two equivalent Mg(1)O4 tetrahedra,  a cornercorner with one Fe(2)O5 trigonal bipyramid, and  an edgeedge with one Fe(2)O5 trigonal bipyramid. The Fe(1)-O(1) bond length is 1.91 Å. The Fe(1)-O(3) bond length is 1.89 Å. The Fe(1)-O(4) bond length is 1.90 Å. The Fe(1)-O(6) bond length is 1.97 Å. In the second Fe site, Fe(2) is bonded to one O(1), one O(2), one O(4), one O(5), and one O(6) atom to form distorted FeO5 trigonal bipyramids that share  a cornercorner with one Fe(1)O4 tetrahedra, corners with three equivalent Mg(1)O4 tetrahedra, and  an edgeedge with one Fe(1)O4 tetrahedra. The Fe(2)-O(1) bond length is 2.09 Å. The Fe(2)-O(2) bond length is 1.90 Å. The Fe(2)-O(4) bond length is 2.17 Å. The Fe(2)-O(5) bond length is 1.92 Å. The Fe(2)-O(6) bond length is 2.29 Å. There are six inequivalent O sites. In the first O site, O(1) is bonded in a 6-coordinate geometry to one Na(1), one Na(2), one Na(3), one Na(4), one Fe(1), and one Fe(2) atom. In the second O site, O(2) is bonded to one Na(1), one Na(3), one Na(4), one Mg(1), and one Fe(2) atom to form a mixture of distorted corner and edge-sharing ONa3MgFe trigonal bipyramids. In the third O site, O(3) is bonded in a 5-coordinate geometry to one Na(1), one Na(2), one Na(3), one Mg(1), and one Fe(1) atom. In the fourth O site, O(4) is bonded in a 6-coordinate geometry to one Na(1), one Na(2), one Na(3), one Na(4), one Fe(1), and one Fe(2) atom. In the fifth O site, O(5) is bonded to one Na(1), one Na(2), one Na(4), one Mg(1), and one Fe(2) atom to form a mixture of corner and edge-sharing ONa3MgFe trigonal bipyramids. In the sixth O site, O(6) is bonded in a 6-coordinate geometry to one Na(1), one Na(2), one Na(4), one Mg(1), one Fe(1), and one Fe(2) atom.