Na8Mg(CoO4)2 crystallizes in the triclinic P1 space group. There are eight inequivalent Na sites. In the first Na site, Na(1) is bonded in a distorted rectangular see-saw-like geometry to one O(1), one O(2), one O(3), and one O(8) atom. In the second Na site, Na(2) is bonded to one O(1), one O(5), one O(6), and one O(8) atom to form distorted NaO4 trigonal pyramids that share  a cornercorner with one Mg(1)O4 tetrahedra,  a cornercorner with one Co(2)O4 tetrahedra, corners with two equivalent Na(8)O4 tetrahedra, corners with three equivalent Co(1)O4 tetrahedra,  a cornercorner with one Na(6)O5 trigonal bipyramid, and  an edgeedge with one Na(6)O5 trigonal bipyramid. In the third Na site, Na(3) is bonded in a 5-coordinate geometry to one O(1), one O(2), one O(3), one O(4), and one O(8) atom. In the fourth Na site, Na(4) is bonded in a 4-coordinate geometry to one O(4), one O(5), one O(6), and one O(7) atom. In the fifth Na site, Na(5) is bonded in a 4-coordinate geometry to one O(2), one O(3), one O(4), one O(5), and one O(7) atom. In the sixth Na site, Na(6) is bonded to one O(1), one O(2), one O(3), one O(6), and one O(8) atom to form distorted NaO5 trigonal bipyramids that share  a cornercorner with one Na(8)O4 tetrahedra,  a cornercorner with one Mg(1)O4 tetrahedra,  a cornercorner with one Co(1)O4 tetrahedra,  a cornercorner with one Na(2)O4 trigonal pyramid,  an edgeedge with one Co(1)O4 tetrahedra,  an edgeedge with one Co(2)O4 tetrahedra, and  an edgeedge with one Na(2)O4 trigonal pyramid. In the seventh Na site, Na(7) is bonded in a rectangular see-saw-like geometry to one O(1), one O(2), one O(6), and one O(8) atom. In the eighth Na site, Na(8) is bonded to one O(4), one O(5), one O(6), and one O(7) atom to form distorted NaO4 tetrahedra that share corners with two equivalent Co(1)O4 tetrahedra, corners with two equivalent Co(2)O4 tetrahedra, corners with three equivalent Mg(1)O4 tetrahedra,  a cornercorner with one Na(6)O5 trigonal bipyramid, and corners with two equivalent Na(2)O4 trigonal pyramids. Mg(1) is bonded to one O(3), one O(4), one O(5), and one O(7) atom to form distorted MgO4 tetrahedra that share  a cornercorner with one Co(1)O4 tetrahedra,  a cornercorner with one Co(2)O4 tetrahedra, corners with three equivalent Na(8)O4 tetrahedra,  a cornercorner with one Na(6)O5 trigonal bipyramid,  a cornercorner with one Na(2)O4 trigonal pyramid, and  an edgeedge with one Co(2)O4 tetrahedra. There are two inequivalent Co sites. In the first Co site, Co(1) is bonded to one O(1), one O(6), one O(7), and one O(8) atom to form CoO4 tetrahedra that share  a cornercorner with one Mg(1)O4 tetrahedra, corners with two equivalent Na(8)O4 tetrahedra,  a cornercorner with one Na(6)O5 trigonal bipyramid, corners with three equivalent Na(2)O4 trigonal pyramids, and  an edgeedge with one Na(6)O5 trigonal bipyramid. In the second Co site, Co(2) is bonded to one O(2), one O(3), one O(4), and one O(5) atom to form CoO4 tetrahedra that share  a cornercorner with one Mg(1)O4 tetrahedra, corners with two equivalent Na(8)O4 tetrahedra,  a cornercorner with one Na(2)O4 trigonal pyramid,  an edgeedge with one Mg(1)O4 tetrahedra, and  an edgeedge with one Na(6)O5 trigonal bipyramid. There are eight 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(6), one Na(7), and one Co(1) atom. In the second O site, O(2) is bonded to one Na(1), one Na(3), one Na(5), one Na(6), one Na(7), and one Co(2) atom to form a mixture of distorted edge and corner-sharing ONa5Co octahedra. The corner-sharing octahedral tilt angles are 11°. In the third O site, O(3) is bonded in a 6-coordinate geometry to one Na(1), one Na(3), one Na(5), one Na(6), 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(3), one Na(4), one Na(5), one Na(8), one Mg(1), and one Co(2) atom. In the fifth O site, O(5) is bonded in a 6-coordinate geometry to one Na(2), one Na(4), one Na(5), one Na(8), one Mg(1), and one Co(2) atom. In the sixth O site, O(6) is bonded to one Na(2), one Na(4), one Na(6), one Na(7), one Na(8), and one Co(1) atom to form a mixture of edge and corner-sharing ONa5Co octahedra. The corner-sharing octahedral tilt angles are 11°. In the seventh O site, O(7) is bonded in a 5-coordinate geometry to one Na(4), one Na(5), one Na(8), one Mg(1), and one Co(1) atom. In the eighth O site, O(8) is bonded to one Na(1), one Na(2), one Na(3), one Na(6), one Na(7), and one Co(1) atom to form edge-sharing ONa5Co octahedra.
Na8Mg(CoO4)2 crystallizes in the triclinic P1 space group. There are eight inequivalent Na sites. In the first Na site, Na(1) is bonded in a distorted rectangular see-saw-like geometry to one O(1), one O(2), one O(3), and one O(8) atom. The Na(1)-O(1) bond length is 2.47 Å. The Na(1)-O(2) bond length is 2.41 Å. The Na(1)-O(3) bond length is 2.47 Å. The Na(1)-O(8) bond length is 2.30 Å. In the second Na site, Na(2) is bonded to one O(1), one O(5), one O(6), and one O(8) atom to form distorted NaO4 trigonal pyramids that share  a cornercorner with one Mg(1)O4 tetrahedra,  a cornercorner with one Co(2)O4 tetrahedra, corners with two equivalent Na(8)O4 tetrahedra, corners with three equivalent Co(1)O4 tetrahedra,  a cornercorner with one Na(6)O5 trigonal bipyramid, and  an edgeedge with one Na(6)O5 trigonal bipyramid. The Na(2)-O(1) bond length is 2.39 Å. The Na(2)-O(5) bond length is 2.41 Å. The Na(2)-O(6) bond length is 2.30 Å. The Na(2)-O(8) bond length is 2.23 Å. In the third Na site, Na(3) is bonded in a 5-coordinate geometry to one O(1), one O(2), one O(3), one O(4), and one O(8) atom. The Na(3)-O(1) bond length is 2.45 Å. The Na(3)-O(2) bond length is 2.46 Å. The Na(3)-O(3) bond length is 2.70 Å. The Na(3)-O(4) bond length is 2.53 Å. The Na(3)-O(8) bond length is 2.34 Å. In the fourth Na site, Na(4) is bonded in a 4-coordinate geometry to one O(4), one O(5), one O(6), and one O(7) atom. The Na(4)-O(4) bond length is 2.58 Å. The Na(4)-O(5) bond length is 2.49 Å. The Na(4)-O(6) bond length is 2.32 Å. The Na(4)-O(7) bond length is 2.36 Å. In the fifth Na site, Na(5) is bonded in a 4-coordinate geometry to one O(2), one O(3), one O(4), one O(5), and one O(7) atom. The Na(5)-O(2) bond length is 2.22 Å. The Na(5)-O(3) bond length is 2.36 Å. The Na(5)-O(4) bond length is 2.49 Å. The Na(5)-O(5) bond length is 2.89 Å. The Na(5)-O(7) bond length is 2.53 Å. In the sixth Na site, Na(6) is bonded to one O(1), one O(2), one O(3), one O(6), and one O(8) atom to form distorted NaO5 trigonal bipyramids that share  a cornercorner with one Na(8)O4 tetrahedra,  a cornercorner with one Mg(1)O4 tetrahedra,  a cornercorner with one Co(1)O4 tetrahedra,  a cornercorner with one Na(2)O4 trigonal pyramid,  an edgeedge with one Co(1)O4 tetrahedra,  an edgeedge with one Co(2)O4 tetrahedra, and  an edgeedge with one Na(2)O4 trigonal pyramid. The Na(6)-O(1) bond length is 2.39 Å. The Na(6)-O(2) bond length is 2.34 Å. The Na(6)-O(3) bond length is 2.62 Å. The Na(6)-O(6) bond length is 2.38 Å. The Na(6)-O(8) bond length is 2.39 Å. In the seventh Na site, Na(7) is bonded in a rectangular see-saw-like geometry to one O(1), one O(2), one O(6), and one O(8) atom. The Na(7)-O(1) bond length is 2.42 Å. The Na(7)-O(2) bond length is 2.35 Å. The Na(7)-O(6) bond length is 2.36 Å. The Na(7)-O(8) bond length is 2.35 Å. In the eighth Na site, Na(8) is bonded to one O(4), one O(5), one O(6), and one O(7) atom to form distorted NaO4 tetrahedra that share corners with two equivalent Co(1)O4 tetrahedra, corners with two equivalent Co(2)O4 tetrahedra, corners with three equivalent Mg(1)O4 tetrahedra,  a cornercorner with one Na(6)O5 trigonal bipyramid, and corners with two equivalent Na(2)O4 trigonal pyramids. The Na(8)-O(4) bond length is 2.56 Å. The Na(8)-O(5) bond length is 2.44 Å. The Na(8)-O(6) bond length is 2.36 Å. The Na(8)-O(7) bond length is 2.46 Å. Mg(1) is bonded to one O(3), one O(4), one O(5), and one O(7) atom to form distorted MgO4 tetrahedra that share  a cornercorner with one Co(1)O4 tetrahedra,  a cornercorner with one Co(2)O4 tetrahedra, corners with three equivalent Na(8)O4 tetrahedra,  a cornercorner with one Na(6)O5 trigonal bipyramid,  a cornercorner with one Na(2)O4 trigonal pyramid, and  an edgeedge with one Co(2)O4 tetrahedra. The Mg(1)-O(3) bond length is 2.03 Å. The Mg(1)-O(4) bond length is 2.00 Å. The Mg(1)-O(5) bond length is 1.98 Å. The Mg(1)-O(7) bond length is 2.01 Å. There are two inequivalent Co sites. In the first Co site, Co(1) is bonded to one O(1), one O(6), one O(7), and one O(8) atom to form CoO4 tetrahedra that share  a cornercorner with one Mg(1)O4 tetrahedra, corners with two equivalent Na(8)O4 tetrahedra,  a cornercorner with one Na(6)O5 trigonal bipyramid, corners with three equivalent Na(2)O4 trigonal pyramids, and  an edgeedge with one Na(6)O5 trigonal bipyramid. The Co(1)-O(1) bond length is 1.92 Å. The Co(1)-O(6) bond length is 1.86 Å. The Co(1)-O(7) bond length is 1.95 Å. The Co(1)-O(8) bond length is 1.88 Å. In the second Co site, Co(2) is bonded to one O(2), one O(3), one O(4), and one O(5) atom to form CoO4 tetrahedra that share  a cornercorner with one Mg(1)O4 tetrahedra, corners with two equivalent Na(8)O4 tetrahedra,  a cornercorner with one Na(2)O4 trigonal pyramid,  an edgeedge with one Mg(1)O4 tetrahedra, and  an edgeedge with one Na(6)O5 trigonal bipyramid. The Co(2)-O(2) bond length is 1.81 Å. The Co(2)-O(3) bond length is 1.95 Å. The Co(2)-O(4) bond length is 1.84 Å. The Co(2)-O(5) bond length is 2.00 Å. There are eight 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(6), one Na(7), and one Co(1) atom. In the second O site, O(2) is bonded to one Na(1), one Na(3), one Na(5), one Na(6), one Na(7), and one Co(2) atom to form a mixture of distorted edge and corner-sharing ONa5Co octahedra. The corner-sharing octahedral tilt angles are 11°. In the third O site, O(3) is bonded in a 6-coordinate geometry to one Na(1), one Na(3), one Na(5), one Na(6), 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(3), one Na(4), one Na(5), one Na(8), one Mg(1), and one Co(2) atom. In the fifth O site, O(5) is bonded in a 6-coordinate geometry to one Na(2), one Na(4), one Na(5), one Na(8), one Mg(1), and one Co(2) atom. In the sixth O site, O(6) is bonded to one Na(2), one Na(4), one Na(6), one Na(7), one Na(8), and one Co(1) atom to form a mixture of edge and corner-sharing ONa5Co octahedra. The corner-sharing octahedral tilt angles are 11°. In the seventh O site, O(7) is bonded in a 5-coordinate geometry to one Na(4), one Na(5), one Na(8), one Mg(1), and one Co(1) atom. In the eighth O site, O(8) is bonded to one Na(1), one Na(2), one Na(3), one Na(6), one Na(7), and one Co(1) atom to form edge-sharing ONa5Co octahedra.