Na8MgMn2O8 crystallizes in the triclinic P1 space group. There are eight 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(4), and one O(7) atom. In the second Na site, Na(2) is bonded to one O(1), one O(2), one O(3), one O(4), and one O(7) atom to form distorted NaO5 trigonal bipyramids that share  a cornercorner with one Mg(1)O4 tetrahedra,  a cornercorner with one Mn(2)O4 tetrahedra,  a cornercorner with one Na(8)O4 trigonal pyramid, edges with two equivalent Na(3)O5 square pyramids,  an edgeedge with one Mn(1)O4 tetrahedra,  an edgeedge with one Mn(2)O4 tetrahedra, and  an edgeedge with one Na(8)O4 trigonal pyramid. 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  a cornercorner with one Mg(1)O4 tetrahedra,  a cornercorner with one Mn(1)O4 tetrahedra, corners with two equivalent Mn(2)O4 tetrahedra,  an edgeedge with one Mn(1)O4 tetrahedra, edges with two equivalent Na(2)O5 trigonal bipyramids, and  an edgeedge with one Na(8)O4 trigonal pyramid. In the fourth Na site, Na(4) is bonded in a distorted rectangular see-saw-like geometry to one O(1), one O(2), one O(3), and one O(4) atom. In the fifth Na site, Na(5) is bonded in a 4-coordinate geometry to one O(3), one O(4), one O(5), and one O(8) atom. In the sixth Na site, Na(6) is bonded in a 3-coordinate geometry to one O(3), one O(5), one O(6), and one O(8) atom. In the seventh Na site, Na(7) is bonded in a distorted trigonal non-coplanar geometry to one O(6), one O(7), and one O(8) atom. In the eighth Na site, Na(8) is bonded to one O(1), one O(2), one O(6), and one O(7) atom to form distorted NaO4 trigonal pyramids that share  a cornercorner with one Mn(1)O4 tetrahedra, corners with three equivalent Mn(2)O4 tetrahedra,  a cornercorner with one Na(2)O5 trigonal bipyramid,  an edgeedge with one Na(3)O5 square pyramid,  an edgeedge with one Mg(1)O4 tetrahedra, and  an edgeedge with one Na(2)O5 trigonal bipyramid. Mg(1) is bonded to one O(5), one O(6), one O(7), and one O(8) atom to form distorted MgO4 tetrahedra that share  a cornercorner with one Na(3)O5 square pyramid, corners with two equivalent Mn(2)O4 tetrahedra,  a cornercorner with one Na(2)O5 trigonal bipyramid,  an edgeedge with one Mn(1)O4 tetrahedra, and  an edgeedge with one Na(8)O4 trigonal pyramid. There are two inequivalent Mn sites. In the first Mn site, Mn(1) is bonded to one O(3), one O(4), one O(5), and one O(6) atom to form distorted MnO4 tetrahedra that share  a cornercorner with one Na(3)O5 square pyramid,  a cornercorner with one Na(8)O4 trigonal pyramid,  an edgeedge with one Na(3)O5 square pyramid,  an edgeedge with one Mg(1)O4 tetrahedra, and  an edgeedge with one Na(2)O5 trigonal bipyramid. In the second Mn site, Mn(2) is bonded to one O(1), one O(2), one O(7), and one O(8) atom to form MnO4 tetrahedra that share corners with two equivalent Na(3)O5 square pyramids, corners with two equivalent Mg(1)O4 tetrahedra,  a cornercorner with one Na(2)O5 trigonal bipyramid, corners with three equivalent Na(8)O4 trigonal pyramids, and  an edgeedge with one Na(2)O5 trigonal bipyramid. There are eight inequivalent O sites. In the first O site, O(1) is bonded to one Na(1), one Na(2), one Na(3), one Na(4), one Na(8), and one Mn(2) atom to form distorted ONa5Mn octahedra that share  a cornercorner with one O(6)Na3MgMn trigonal bipyramid and edges with two equivalent O(4)Na5Mn octahedra. In the second O site, O(2) is bonded in a 6-coordinate geometry to one Na(1), one Na(2), one Na(3), one Na(4), one Na(8), and one Mn(2) atom. In the third O site, O(3) is bonded in a 7-coordinate geometry to one Na(1), one Na(2), one Na(3), one Na(4), one Na(5), one Na(6), and one Mn(1) atom. In the fourth O site, O(4) is bonded to one Na(1), one Na(2), one Na(3), one Na(4), one Na(5), and one Mn(1) atom to form ONa5Mn octahedra that share  a cornercorner with one O(6)Na3MgMn trigonal bipyramid and edges with two equivalent O(1)Na5Mn octahedra. In the fifth O site, O(5) is bonded in a 5-coordinate geometry to one Na(3), one Na(5), one Na(6), one Mg(1), and one Mn(1) atom. In the sixth O site, O(6) is bonded to one Na(6), one Na(7), one Na(8), one Mg(1), and one Mn(1) atom to form distorted corner-sharing ONa3MgMn trigonal bipyramids. The corner-sharing octahedral tilt angles range from 57-68°. In the seventh O site, O(7) is bonded in a 5-coordinate geometry to one Na(1), one Na(2), one Na(7), one Na(8), one Mg(1), and one Mn(2) atom. In the eighth O site, O(8) is bonded in a 5-coordinate geometry to one Na(5), one Na(6), one Na(7), one Mg(1), and one Mn(2) atom.
Na8MgMn2O8 crystallizes in the triclinic P1 space group. There are eight 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(4), and one O(7) atom. The Na(1)-O(1) bond length is 2.29 Å. The Na(1)-O(2) bond length is 2.33 Å. The Na(1)-O(3) bond length is 2.75 Å. The Na(1)-O(4) bond length is 2.36 Å. The Na(1)-O(7) bond length is 2.93 Å. In the second Na site, Na(2) is bonded to one O(1), one O(2), one O(3), one O(4), and one O(7) atom to form distorted NaO5 trigonal bipyramids that share  a cornercorner with one Mg(1)O4 tetrahedra,  a cornercorner with one Mn(2)O4 tetrahedra,  a cornercorner with one Na(8)O4 trigonal pyramid, edges with two equivalent Na(3)O5 square pyramids,  an edgeedge with one Mn(1)O4 tetrahedra,  an edgeedge with one Mn(2)O4 tetrahedra, and  an edgeedge with one Na(8)O4 trigonal pyramid. The Na(2)-O(1) bond length is 2.46 Å. The Na(2)-O(2) bond length is 2.58 Å. The Na(2)-O(3) bond length is 2.60 Å. The Na(2)-O(4) bond length is 2.31 Å. The Na(2)-O(7) bond length is 2.44 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  a cornercorner with one Mg(1)O4 tetrahedra,  a cornercorner with one Mn(1)O4 tetrahedra, corners with two equivalent Mn(2)O4 tetrahedra,  an edgeedge with one Mn(1)O4 tetrahedra, edges with two equivalent Na(2)O5 trigonal bipyramids, and  an edgeedge with one Na(8)O4 trigonal pyramid. The Na(3)-O(1) bond length is 2.52 Å. The Na(3)-O(2) bond length is 2.72 Å. The Na(3)-O(3) bond length is 2.43 Å. The Na(3)-O(4) bond length is 2.40 Å. The Na(3)-O(5) bond length is 2.38 Å. In the fourth Na site, Na(4) is bonded in a distorted rectangular see-saw-like geometry to one O(1), one O(2), one O(3), and one O(4) atom. The Na(4)-O(1) bond length is 2.32 Å. The Na(4)-O(2) bond length is 2.31 Å. The Na(4)-O(3) bond length is 2.54 Å. The Na(4)-O(4) bond length is 2.37 Å. In the fifth Na site, Na(5) is bonded in a 4-coordinate geometry to one O(3), one O(4), one O(5), and one O(8) atom. The Na(5)-O(3) bond length is 2.34 Å. The Na(5)-O(4) bond length is 2.27 Å. The Na(5)-O(5) bond length is 2.54 Å. The Na(5)-O(8) bond length is 2.54 Å. In the sixth Na site, Na(6) is bonded in a 3-coordinate geometry to one O(3), one O(5), one O(6), and one O(8) atom. The Na(6)-O(3) bond length is 2.77 Å. The Na(6)-O(5) bond length is 2.29 Å. The Na(6)-O(6) bond length is 2.17 Å. The Na(6)-O(8) bond length is 2.34 Å. In the seventh Na site, Na(7) is bonded in a distorted trigonal non-coplanar geometry to one O(6), one O(7), and one O(8) atom. The Na(7)-O(6) bond length is 2.34 Å. The Na(7)-O(7) bond length is 2.41 Å. The Na(7)-O(8) bond length is 2.46 Å. In the eighth Na site, Na(8) is bonded to one O(1), one O(2), one O(6), and one O(7) atom to form distorted NaO4 trigonal pyramids that share  a cornercorner with one Mn(1)O4 tetrahedra, corners with three equivalent Mn(2)O4 tetrahedra,  a cornercorner with one Na(2)O5 trigonal bipyramid,  an edgeedge with one Na(3)O5 square pyramid,  an edgeedge with one Mg(1)O4 tetrahedra, and  an edgeedge with one Na(2)O5 trigonal bipyramid. The Na(8)-O(1) bond length is 2.30 Å. The Na(8)-O(2) bond length is 2.21 Å. The Na(8)-O(6) bond length is 2.42 Å. The Na(8)-O(7) bond length is 2.44 Å. Mg(1) is bonded to one O(5), one O(6), one O(7), and one O(8) atom to form distorted MgO4 tetrahedra that share  a cornercorner with one Na(3)O5 square pyramid, corners with two equivalent Mn(2)O4 tetrahedra,  a cornercorner with one Na(2)O5 trigonal bipyramid,  an edgeedge with one Mn(1)O4 tetrahedra, and  an edgeedge with one Na(8)O4 trigonal pyramid. The Mg(1)-O(5) bond length is 2.02 Å. The Mg(1)-O(6) bond length is 1.99 Å. The Mg(1)-O(7) bond length is 1.99 Å. The Mg(1)-O(8) bond length is 2.01 Å. There are two inequivalent Mn sites. In the first Mn site, Mn(1) is bonded to one O(3), one O(4), one O(5), and one O(6) atom to form distorted MnO4 tetrahedra that share  a cornercorner with one Na(3)O5 square pyramid,  a cornercorner with one Na(8)O4 trigonal pyramid,  an edgeedge with one Na(3)O5 square pyramid,  an edgeedge with one Mg(1)O4 tetrahedra, and  an edgeedge with one Na(2)O5 trigonal bipyramid. The Mn(1)-O(3) bond length is 1.91 Å. The Mn(1)-O(4) bond length is 1.88 Å. The Mn(1)-O(5) bond length is 1.93 Å. The Mn(1)-O(6) bond length is 2.03 Å. In the second Mn site, Mn(2) is bonded to one O(1), one O(2), one O(7), and one O(8) atom to form MnO4 tetrahedra that share corners with two equivalent Na(3)O5 square pyramids, corners with two equivalent Mg(1)O4 tetrahedra,  a cornercorner with one Na(2)O5 trigonal bipyramid, corners with three equivalent Na(8)O4 trigonal pyramids, and  an edgeedge with one Na(2)O5 trigonal bipyramid. The Mn(2)-O(1) bond length is 1.90 Å. The Mn(2)-O(2) bond length is 1.88 Å. The Mn(2)-O(7) bond length is 2.03 Å. The Mn(2)-O(8) bond length is 2.02 Å. There are eight inequivalent O sites. In the first O site, O(1) is bonded to one Na(1), one Na(2), one Na(3), one Na(4), one Na(8), and one Mn(2) atom to form distorted ONa5Mn octahedra that share  a cornercorner with one O(6)Na3MgMn trigonal bipyramid and edges with two equivalent O(4)Na5Mn octahedra. In the second O site, O(2) is bonded in a 6-coordinate geometry to one Na(1), one Na(2), one Na(3), one Na(4), one Na(8), and one Mn(2) atom. In the third O site, O(3) is bonded in a 7-coordinate geometry to one Na(1), one Na(2), one Na(3), one Na(4), one Na(5), one Na(6), and one Mn(1) atom. In the fourth O site, O(4) is bonded to one Na(1), one Na(2), one Na(3), one Na(4), one Na(5), and one Mn(1) atom to form ONa5Mn octahedra that share  a cornercorner with one O(6)Na3MgMn trigonal bipyramid and edges with two equivalent O(1)Na5Mn octahedra. In the fifth O site, O(5) is bonded in a 5-coordinate geometry to one Na(3), one Na(5), one Na(6), one Mg(1), and one Mn(1) atom. In the sixth O site, O(6) is bonded to one Na(6), one Na(7), one Na(8), one Mg(1), and one Mn(1) atom to form distorted corner-sharing ONa3MgMn trigonal bipyramids. The corner-sharing octahedral tilt angles range from 57-68°. In the seventh O site, O(7) is bonded in a 5-coordinate geometry to one Na(1), one Na(2), one Na(7), one Na(8), one Mg(1), and one Mn(2) atom. In the eighth O site, O(8) is bonded in a 5-coordinate geometry to one Na(5), one Na(6), one Na(7), one Mg(1), and one Mn(2) atom.