Na4Mg(CoO3)2 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(2), one O(3), one O(4), one O(5), and one O(6) atom to form distorted NaO5 trigonal bipyramids that share  a cornercorner with one Co(2)O4 tetrahedra, corners with three equivalent Mg(1)O4 tetrahedra, and  an edgeedge with one Co(2)O4 tetrahedra. In the second Na site, Na(2) 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. In the third Na site, Na(3) is bonded in a distorted see-saw-like geometry to one O(1), one O(4), one O(5), and one O(6) atom. In the fourth Na site, Na(4) is bonded in a 5-coordinate geometry to one O(1), one O(2), one O(3), one O(4), and one O(6) atom. Mg(1) is bonded to one O(1), one O(2), one O(3), and one O(6) atom to form distorted MgO4 tetrahedra that share corners with two equivalent Co(2)O4 tetrahedra and corners with three equivalent Na(1)O5 trigonal bipyramids. There are two inequivalent Co sites. In the first Co site, Co(1) is bonded in a trigonal planar geometry to one O(2), one O(4), and one O(5) atom. In the second Co site, Co(2) is bonded to one O(1), one O(3), one O(4), and one O(5) atom to form CoO4 tetrahedra that share corners with two equivalent Mg(1)O4 tetrahedra,  a cornercorner with one Na(1)O5 trigonal bipyramid, and  an edgeedge with one Na(1)O5 trigonal bipyramid. There are six inequivalent O sites. In the first O site, O(1) is bonded to one Na(3), one Na(4), one Mg(1), and one Co(2) atom to form distorted ONa2MgCo trigonal pyramids that share  a cornercorner with one O(6)Na4Mg trigonal bipyramid,  an edgeedge with one O(5)Na3Co2 square pyramid, and  an edgeedge with one O(6)Na4Mg trigonal bipyramid. In the second O site, O(2) is bonded in a 5-coordinate geometry to one Na(1), one Na(2), one Na(4), one Mg(1), and one Co(1) atom. In the third O site, O(3) is bonded in a 5-coordinate geometry to one Na(1), one Na(2), one Na(4), one Mg(1), and one Co(2) 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 Co(1), and one Co(2) atom. In the fifth O site, O(5) is bonded to one Na(1), one Na(2), one Na(3), one Co(1), and one Co(2) atom to form distorted ONa3Co2 square pyramids that share  a cornercorner with one O(6)Na4Mg trigonal bipyramid,  an edgeedge with one O(6)Na4Mg trigonal bipyramid, and  an edgeedge with one O(1)Na2MgCo trigonal pyramid. In the sixth O site, O(6) is bonded to one Na(1), one Na(2), one Na(3), one Na(4), and one Mg(1) atom to form ONa4Mg trigonal bipyramids that share  a cornercorner with one O(5)Na3Co2 square pyramid,  a cornercorner with one O(1)Na2MgCo trigonal pyramid,  an edgeedge with one O(5)Na3Co2 square pyramid, and  an edgeedge with one O(1)Na2MgCo trigonal pyramid.
Na4Mg(CoO3)2 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(2), one O(3), one O(4), one O(5), and one O(6) atom to form distorted NaO5 trigonal bipyramids that share  a cornercorner with one Co(2)O4 tetrahedra, corners with three equivalent Mg(1)O4 tetrahedra, and  an edgeedge with one Co(2)O4 tetrahedra. The Na(1)-O(2) bond length is 2.72 Å. The Na(1)-O(3) bond length is 2.74 Å. The Na(1)-O(4) bond length is 2.64 Å. The Na(1)-O(5) bond length is 2.47 Å. The Na(1)-O(6) bond length is 2.27 Å. In the second Na site, Na(2) 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(2)-O(2) bond length is 2.52 Å. The Na(2)-O(3) bond length is 2.42 Å. The Na(2)-O(4) bond length is 2.84 Å. The Na(2)-O(5) bond length is 2.60 Å. The Na(2)-O(6) bond length is 2.32 Å. In the third Na site, Na(3) is bonded in a distorted see-saw-like geometry to one O(1), one O(4), one O(5), and one O(6) atom. The Na(3)-O(1) bond length is 2.22 Å. The Na(3)-O(4) bond length is 2.31 Å. The Na(3)-O(5) bond length is 2.53 Å. The Na(3)-O(6) bond length is 2.17 Å. In the fourth Na site, Na(4) is bonded in a 5-coordinate geometry to one O(1), one O(2), one O(3), one O(4), and one O(6) atom. The Na(4)-O(1) bond length is 2.46 Å. The Na(4)-O(2) bond length is 2.38 Å. The Na(4)-O(3) bond length is 2.35 Å. The Na(4)-O(4) bond length is 2.49 Å. The Na(4)-O(6) bond length is 2.23 Å. Mg(1) is bonded to one O(1), one O(2), one O(3), and one O(6) atom to form distorted MgO4 tetrahedra that share corners with two equivalent Co(2)O4 tetrahedra and corners with three equivalent Na(1)O5 trigonal bipyramids. The Mg(1)-O(1) bond length is 1.97 Å. The Mg(1)-O(2) bond length is 2.08 Å. The Mg(1)-O(3) bond length is 2.01 Å. The Mg(1)-O(6) bond length is 1.92 Å. There are two inequivalent Co sites. In the first Co site, Co(1) is bonded in a trigonal planar geometry to one O(2), one O(4), and one O(5) atom. The Co(1)-O(2) bond length is 1.79 Å. The Co(1)-O(4) bond length is 1.83 Å. The Co(1)-O(5) bond length is 1.81 Å. In the second Co site, Co(2) is bonded to one O(1), one O(3), one O(4), and one O(5) atom to form CoO4 tetrahedra that share corners with two equivalent Mg(1)O4 tetrahedra,  a cornercorner with one Na(1)O5 trigonal bipyramid, and  an edgeedge with one Na(1)O5 trigonal bipyramid. The Co(2)-O(1) bond length is 1.79 Å. The Co(2)-O(3) bond length is 1.81 Å. The Co(2)-O(4) bond length is 2.00 Å. The Co(2)-O(5) bond length is 1.99 Å. There are six inequivalent O sites. In the first O site, O(1) is bonded to one Na(3), one Na(4), one Mg(1), and one Co(2) atom to form distorted ONa2MgCo trigonal pyramids that share  a cornercorner with one O(6)Na4Mg trigonal bipyramid,  an edgeedge with one O(5)Na3Co2 square pyramid, and  an edgeedge with one O(6)Na4Mg trigonal bipyramid. In the second O site, O(2) is bonded in a 5-coordinate geometry to one Na(1), one Na(2), one Na(4), one Mg(1), and one Co(1) atom. In the third O site, O(3) is bonded in a 5-coordinate geometry to one Na(1), one Na(2), one Na(4), one Mg(1), and one Co(2) 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 Co(1), and one Co(2) atom. In the fifth O site, O(5) is bonded to one Na(1), one Na(2), one Na(3), one Co(1), and one Co(2) atom to form distorted ONa3Co2 square pyramids that share  a cornercorner with one O(6)Na4Mg trigonal bipyramid,  an edgeedge with one O(6)Na4Mg trigonal bipyramid, and  an edgeedge with one O(1)Na2MgCo trigonal pyramid. In the sixth O site, O(6) is bonded to one Na(1), one Na(2), one Na(3), one Na(4), and one Mg(1) atom to form ONa4Mg trigonal bipyramids that share  a cornercorner with one O(5)Na3Co2 square pyramid,  a cornercorner with one O(1)Na2MgCo trigonal pyramid,  an edgeedge with one O(5)Na3Co2 square pyramid, and  an edgeedge with one O(1)Na2MgCo trigonal pyramid.