Na4Mg(CoO3)2 crystallizes in the monoclinic Cm space group. There are four inequivalent Na sites. In the first Na site, Na(1) is bonded in a 3-coordinate geometry to one O(1) and two equivalent O(3) atoms. In the second Na site, Na(2) is bonded in a distorted trigonal bipyramidal geometry to one O(1), two equivalent O(2), and two equivalent O(3) atoms. In the third Na site, Na(3) is bonded in a distorted trigonal planar geometry to one O(1) and two equivalent O(3) atoms. In the fourth Na site, Na(4) is bonded in a 5-coordinate geometry to one O(4), two equivalent O(2), and two equivalent O(3) atoms. Mg(1) is bonded in a trigonal planar geometry to one O(4) and two equivalent O(2) atoms. There are two inequivalent Co sites. In the first Co site, Co(1) is bonded in a trigonal planar geometry to one O(1) and two equivalent O(2) atoms. In the second Co site, Co(2) is bonded in a trigonal planar geometry to one O(4) and two equivalent O(3) atoms. There are four inequivalent O sites. In the first O site, O(1) is bonded in a rectangular see-saw-like geometry to one Na(1), one Na(2), one Na(3), and one Co(1) atom. In the second O site, O(2) is bonded in a 4-coordinate geometry to 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(3), one Na(4), and one Co(2) atom. In the fourth O site, O(4) is bonded in a T-shaped geometry to one Na(4), one Mg(1), and one Co(2) atom.
Na4Mg(CoO3)2 crystallizes in the monoclinic Cm space group. There are four inequivalent Na sites. In the first Na site, Na(1) is bonded in a 3-coordinate geometry to one O(1) and two equivalent O(3) atoms. The Na(1)-O(1) bond length is 2.48 Å. Both Na(1)-O(3) bond lengths are 2.63 Å. In the second Na site, Na(2) is bonded in a distorted trigonal bipyramidal geometry to one O(1), two equivalent O(2), and two equivalent O(3) atoms. The Na(2)-O(1) bond length is 2.47 Å. Both Na(2)-O(2) bond lengths are 2.49 Å. Both Na(2)-O(3) bond lengths are 2.29 Å. In the third Na site, Na(3) is bonded in a distorted trigonal planar geometry to one O(1) and two equivalent O(3) atoms. The Na(3)-O(1) bond length is 2.18 Å. Both Na(3)-O(3) bond lengths are 2.24 Å. In the fourth Na site, Na(4) is bonded in a 5-coordinate geometry to one O(4), two equivalent O(2), and two equivalent O(3) atoms. The Na(4)-O(4) bond length is 2.30 Å. Both Na(4)-O(2) bond lengths are 2.43 Å. Both Na(4)-O(3) bond lengths are 2.48 Å. Mg(1) is bonded in a trigonal planar geometry to one O(4) and two equivalent O(2) atoms. The Mg(1)-O(4) bond length is 1.93 Å. Both Mg(1)-O(2) bond lengths are 1.96 Å. There are two inequivalent Co sites. In the first Co site, Co(1) is bonded in a trigonal planar geometry to one O(1) and two equivalent O(2) atoms. The Co(1)-O(1) bond length is 1.71 Å. Both Co(1)-O(2) bond lengths are 1.81 Å. In the second Co site, Co(2) is bonded in a trigonal planar geometry to one O(4) and two equivalent O(3) atoms. The Co(2)-O(4) bond length is 1.79 Å. Both Co(2)-O(3) bond lengths are 1.77 Å. There are four inequivalent O sites. In the first O site, O(1) is bonded in a rectangular see-saw-like geometry to one Na(1), one Na(2), one Na(3), and one Co(1) atom. In the second O site, O(2) is bonded in a 4-coordinate geometry to 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(3), one Na(4), and one Co(2) atom. In the fourth O site, O(4) is bonded in a T-shaped geometry to one Na(4), one Mg(1), and one Co(2) atom.