Na2Mg(CoO2)2 crystallizes in the triclinic P1 space group. There are two inequivalent Na sites. In the first Na site, Na(1) is bonded to one O(2), one O(3), and two equivalent O(4) atoms to form distorted NaO4 tetrahedra that share corners with four equivalent Mg(1)O5 square pyramids, corners with two equivalent Na(1)O4 tetrahedra, and  an edgeedge with one Co(2)O4 tetrahedra. In the second Na site, Na(2) is bonded in a 6-coordinate geometry to two equivalent O(1), two equivalent O(2), and two equivalent O(4) atoms. Mg(1) is bonded to one O(1), two equivalent O(2), and two equivalent O(3) atoms to form MgO5 square pyramids that share corners with two equivalent Co(2)O4 tetrahedra, corners with four equivalent Na(1)O4 tetrahedra, edges with two equivalent Mg(1)O5 square pyramids, and edges with two equivalent Co(2)O4 tetrahedra. There are two inequivalent Co sites. In the first Co site, Co(1) is bonded in a distorted see-saw-like geometry to one O(1), one O(3), and two equivalent O(4) atoms. In the second Co site, Co(2) is bonded to one O(2), one O(3), and two equivalent O(1) atoms to form distorted CoO4 tetrahedra that share corners with two equivalent Mg(1)O5 square pyramids, corners with two equivalent Co(2)O4 tetrahedra, edges with two equivalent Mg(1)O5 square pyramids, and  an edgeedge with one Na(1)O4 tetrahedra. There are four inequivalent O sites. In the first O site, O(1) is bonded in a 6-coordinate geometry to two equivalent Na(2), one Mg(1), one Co(1), and two equivalent Co(2) atoms. In the second O site, O(2) is bonded in a 6-coordinate geometry to one Na(1), two equivalent Na(2), two equivalent Mg(1), and one Co(2) atom. In the third O site, O(3) is bonded to one Na(1), two equivalent Mg(1), one Co(1), and one Co(2) atom to form distorted ONaMg2Co2 trigonal bipyramids that share corners with four equivalent O(4)Na4Co2 octahedra and corners with two equivalent O(3)NaMg2Co2 trigonal bipyramids. The corner-sharing octahedral tilt angles range from 38-81°. In the fourth O site, O(4) is bonded to two equivalent Na(1), two equivalent Na(2), and two equivalent Co(1) atoms to form distorted ONa4Co2 octahedra that share corners with two equivalent O(4)Na4Co2 octahedra, corners with four equivalent O(3)NaMg2Co2 trigonal bipyramids, and edges with two equivalent O(4)Na4Co2 octahedra. The corner-sharing octahedral tilt angles are 12°.
Na2Mg(CoO2)2 crystallizes in the triclinic P1 space group. There are two inequivalent Na sites. In the first Na site, Na(1) is bonded to one O(2), one O(3), and two equivalent O(4) atoms to form distorted NaO4 tetrahedra that share corners with four equivalent Mg(1)O5 square pyramids, corners with two equivalent Na(1)O4 tetrahedra, and  an edgeedge with one Co(2)O4 tetrahedra. The Na(1)-O(2) bond length is 2.27 Å. The Na(1)-O(3) bond length is 2.35 Å. There is one shorter (2.25 Å) and one longer (2.27 Å) Na(1)-O(4) bond length. In the second Na site, Na(2) is bonded in a 6-coordinate geometry to two equivalent O(1), two equivalent O(2), and two equivalent O(4) atoms. There is one shorter (2.37 Å) and one longer (2.83 Å) Na(2)-O(1) bond length. There is one shorter (2.45 Å) and one longer (2.68 Å) Na(2)-O(2) bond length. There is one shorter (2.62 Å) and one longer (2.69 Å) Na(2)-O(4) bond length. Mg(1) is bonded to one O(1), two equivalent O(2), and two equivalent O(3) atoms to form MgO5 square pyramids that share corners with two equivalent Co(2)O4 tetrahedra, corners with four equivalent Na(1)O4 tetrahedra, edges with two equivalent Mg(1)O5 square pyramids, and edges with two equivalent Co(2)O4 tetrahedra. The Mg(1)-O(1) bond length is 2.11 Å. There is one shorter (2.02 Å) and one longer (2.06 Å) Mg(1)-O(2) bond length. There is one shorter (2.09 Å) and one longer (2.22 Å) Mg(1)-O(3) bond length. There are two inequivalent Co sites. In the first Co site, Co(1) is bonded in a distorted see-saw-like geometry to one O(1), one O(3), and two equivalent O(4) atoms. The Co(1)-O(1) bond length is 2.13 Å. The Co(1)-O(3) bond length is 2.07 Å. Both Co(1)-O(4) bond lengths are 1.97 Å. In the second Co site, Co(2) is bonded to one O(2), one O(3), and two equivalent O(1) atoms to form distorted CoO4 tetrahedra that share corners with two equivalent Mg(1)O5 square pyramids, corners with two equivalent Co(2)O4 tetrahedra, edges with two equivalent Mg(1)O5 square pyramids, and  an edgeedge with one Na(1)O4 tetrahedra. The Co(2)-O(2) bond length is 2.12 Å. The Co(2)-O(3) bond length is 1.95 Å. There is one shorter (2.00 Å) and one longer (2.04 Å) Co(2)-O(1) bond length. There are four inequivalent O sites. In the first O site, O(1) is bonded in a 6-coordinate geometry to two equivalent Na(2), one Mg(1), one Co(1), and two equivalent Co(2) atoms. In the second O site, O(2) is bonded in a 6-coordinate geometry to one Na(1), two equivalent Na(2), two equivalent Mg(1), and one Co(2) atom. In the third O site, O(3) is bonded to one Na(1), two equivalent Mg(1), one Co(1), and one Co(2) atom to form distorted ONaMg2Co2 trigonal bipyramids that share corners with four equivalent O(4)Na4Co2 octahedra and corners with two equivalent O(3)NaMg2Co2 trigonal bipyramids. The corner-sharing octahedral tilt angles range from 38-81°. In the fourth O site, O(4) is bonded to two equivalent Na(1), two equivalent Na(2), and two equivalent Co(1) atoms to form distorted ONa4Co2 octahedra that share corners with two equivalent O(4)Na4Co2 octahedra, corners with four equivalent O(3)NaMg2Co2 trigonal bipyramids, and edges with two equivalent O(4)Na4Co2 octahedra. The corner-sharing octahedral tilt angles are 12°.