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 5-coordinate geometry to one O(1), one O(2), one O(3), 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 to one O(1), one O(2), one O(3), one O(4), and one O(5) atom to form distorted NaO5 square pyramids that share corners with four equivalent Mg(1)O4 trigonal pyramids and edges with two equivalent Fe(2)O5 trigonal bipyramids. In the fourth Na site, Na(4) is bonded in a 5-coordinate geometry to one O(2), one O(3), one O(4), one O(5), and one O(6) atom. Mg(1) is bonded to one O(1), one O(2), one O(3), and one O(4) atom to form distorted MgO4 trigonal pyramids that share corners with four equivalent Na(3)O5 square pyramids 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 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 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 FeO5 trigonal bipyramids that share corners with three equivalent Mg(1)O4 trigonal pyramids and edges with two equivalent Na(3)O5 square pyramids. 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 Mg(1), one Fe(1), and one Fe(2) atom. In the second O site, O(2) is bonded in a 6-coordinate geometry to one Na(1), one Na(3), one Na(4), one Mg(1), one Fe(1), and one Fe(2) atom. In the third O site, O(3) is bonded in a 6-coordinate geometry to one Na(1), one Na(2), one Na(3), one Na(4), 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(2), one Na(3), one Na(4), one Mg(1), 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(3), one Na(4), one Fe(1), and one Fe(2) atom to form a mixture of distorted corner and edge-sharing ONa4Fe2 octahedra. In the sixth O site, O(6) is bonded to one Na(1), one Na(2), one Na(4), one Fe(1), and one Fe(2) atom to form a mixture of corner and edge-sharing ONa3Fe2 trigonal bipyramids. The corner-sharing octahedral tilt angles are 10°.
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 5-coordinate geometry to one O(1), one O(2), one O(3), one O(5), and one O(6) atom. The Na(1)-O(1) bond length is 2.66 Å. The Na(1)-O(2) bond length is 2.44 Å. The Na(1)-O(3) bond length is 2.25 Å. The Na(1)-O(5) bond length is 2.38 Å. The Na(1)-O(6) bond length is 2.22 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 2.45 Å. The Na(2)-O(3) bond length is 2.50 Å. The Na(2)-O(4) bond length is 2.59 Å. The Na(2)-O(5) bond length is 2.37 Å. The Na(2)-O(6) bond length is 2.23 Å. In the third Na site, Na(3) is bonded to one O(1), one O(2), one O(3), one O(4), and one O(5) atom to form distorted NaO5 square pyramids that share corners with four equivalent Mg(1)O4 trigonal pyramids and edges with two equivalent Fe(2)O5 trigonal bipyramids. The Na(3)-O(1) bond length is 2.26 Å. The Na(3)-O(2) bond length is 2.42 Å. The Na(3)-O(3) bond length is 2.29 Å. The Na(3)-O(4) bond length is 2.46 Å. The Na(3)-O(5) bond length is 2.56 Å. In the fourth Na site, Na(4) is bonded in a 5-coordinate geometry to one O(2), one O(3), one O(4), one O(5), and one O(6) atom. The Na(4)-O(2) bond length is 2.30 Å. The Na(4)-O(3) bond length is 2.46 Å. The Na(4)-O(4) bond length is 2.61 Å. The Na(4)-O(5) bond length is 2.28 Å. The Na(4)-O(6) bond length is 2.26 Å. Mg(1) is bonded to one O(1), one O(2), one O(3), and one O(4) atom to form distorted MgO4 trigonal pyramids that share corners with four equivalent Na(3)O5 square pyramids and corners with three equivalent Fe(2)O5 trigonal bipyramids. The Mg(1)-O(1) bond length is 1.99 Å. The Mg(1)-O(2) bond length is 2.04 Å. The Mg(1)-O(3) bond length is 1.99 Å. The Mg(1)-O(4) bond length is 2.01 Å. There are two inequivalent Fe sites. In the first Fe site, Fe(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 Fe(1)-O(1) bond length is 2.56 Å. The Fe(1)-O(2) bond length is 2.20 Å. The Fe(1)-O(3) bond length is 2.06 Å. The Fe(1)-O(4) bond length is 2.04 Å. The Fe(1)-O(5) bond length is 2.04 Å. The Fe(1)-O(6) bond length is 2.00 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 FeO5 trigonal bipyramids that share corners with three equivalent Mg(1)O4 trigonal pyramids and edges with two equivalent Na(3)O5 square pyramids. The Fe(2)-O(1) bond length is 2.00 Å. The Fe(2)-O(2) bond length is 2.00 Å. The Fe(2)-O(4) bond length is 2.11 Å. The Fe(2)-O(5) bond length is 2.06 Å. The Fe(2)-O(6) bond length is 2.00 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 Mg(1), one Fe(1), and one Fe(2) atom. In the second O site, O(2) is bonded in a 6-coordinate geometry to one Na(1), one Na(3), one Na(4), one Mg(1), one Fe(1), and one Fe(2) atom. In the third O site, O(3) is bonded in a 6-coordinate geometry to one Na(1), one Na(2), one Na(3), one Na(4), 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(2), one Na(3), one Na(4), one Mg(1), 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(3), one Na(4), one Fe(1), and one Fe(2) atom to form a mixture of distorted corner and edge-sharing ONa4Fe2 octahedra. In the sixth O site, O(6) is bonded to one Na(1), one Na(2), one Na(4), one Fe(1), and one Fe(2) atom to form a mixture of corner and edge-sharing ONa3Fe2 trigonal bipyramids. The corner-sharing octahedral tilt angles are 10°.