Na4Mg(NiO3)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(1), one O(2), one O(4), and one O(6) atom to form distorted NaO4 tetrahedra that share  a cornercorner with one Na(2)O5 square pyramid, corners with three equivalent Ni(2)O4 tetrahedra, and  an edgeedge with one Na(2)O5 square pyramid. In the second Na site, Na(2) is bonded to one O(1), one O(2), one O(3), one O(5), and one O(6) atom to form distorted NaO5 square pyramids that share  a cornercorner with one Na(1)O4 tetrahedra,  a cornercorner with one Ni(2)O4 tetrahedra,  an edgeedge with one Na(1)O4 tetrahedra, and  an edgeedge with one Ni(2)O4 tetrahedra. In the third Na site, Na(3) is bonded in a 5-coordinate geometry to one O(1), one O(2), one O(4), one O(5), and one O(6) atom. In the fourth Na site, Na(4) is bonded in a 4-coordinate geometry to one O(1), one O(3), one O(5), and one O(6) atom. Mg(1) is bonded in a rectangular see-saw-like geometry to one O(1), one O(3), one O(4), and one O(5) atom. There are two inequivalent Ni sites. In the first Ni site, Ni(1) is bonded in a 5-coordinate geometry to one O(1), one O(2), one O(4), one O(5), and one O(6) atom. In the second Ni site, Ni(2) is bonded to one O(2), one O(3), one O(4), and one O(6) atom to form NiO4 tetrahedra that share  a cornercorner with one Na(2)O5 square pyramid, corners with three equivalent Na(1)O4 tetrahedra, and  an edgeedge with one Na(2)O5 square pyramid. There are six 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 Mg(1), and one Ni(1) atom to form distorted ONa4MgNi octahedra that share corners with three equivalent O(3)Na2MgNi tetrahedra, corners with two equivalent O(2)Na3Ni2 trigonal bipyramids, corners with three equivalent O(5)Na3MgNi trigonal bipyramids,  an edgeedge with one O(5)Na3MgNi trigonal bipyramid, and  an edgeedge with one O(2)Na3Ni2 trigonal bipyramid. In the second O site, O(2) is bonded to one Na(1), one Na(2), one Na(3), one Ni(1), and one Ni(2) atom to form distorted ONa3Ni2 trigonal bipyramids that share corners with two equivalent O(1)Na4MgNi octahedra, corners with two equivalent O(3)Na2MgNi tetrahedra,  a cornercorner with one O(5)Na3MgNi trigonal bipyramid,  an edgeedge with one O(1)Na4MgNi octahedra, and  an edgeedge with one O(5)Na3MgNi trigonal bipyramid. The corner-sharing octahedral tilt angles range from 8-71°. In the third O site, O(3) is bonded to one Na(2), one Na(4), one Mg(1), and one Ni(2) atom to form ONa2MgNi tetrahedra that share corners with three equivalent O(1)Na4MgNi octahedra, corners with two equivalent O(2)Na3Ni2 trigonal bipyramids, and corners with three equivalent O(5)Na3MgNi trigonal bipyramids. The corner-sharing octahedral tilt angles range from 57-69°. In the fourth O site, O(4) is bonded in a 5-coordinate geometry to one Na(1), one Na(3), one Mg(1), one Ni(1), and one Ni(2) atom. In the fifth O site, O(5) is bonded to one Na(2), one Na(3), one Na(4), one Mg(1), and one Ni(1) atom to form distorted ONa3MgNi trigonal bipyramids that share corners with three equivalent O(1)Na4MgNi octahedra, corners with three equivalent O(3)Na2MgNi tetrahedra,  a cornercorner with one O(2)Na3Ni2 trigonal bipyramid,  an edgeedge with one O(1)Na4MgNi octahedra, and  an edgeedge with one O(2)Na3Ni2 trigonal bipyramid. The corner-sharing octahedral tilt angles range from 17-64°. In the sixth O site, O(6) is bonded in a 6-coordinate geometry to one Na(1), one Na(2), one Na(3), one Na(4), one Ni(1), and one Ni(2) atom.
Na4Mg(NiO3)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(1), one O(2), one O(4), and one O(6) atom to form distorted NaO4 tetrahedra that share  a cornercorner with one Na(2)O5 square pyramid, corners with three equivalent Ni(2)O4 tetrahedra, and  an edgeedge with one Na(2)O5 square pyramid. The Na(1)-O(1) bond length is 2.40 Å. The Na(1)-O(2) bond length is 2.34 Å. The Na(1)-O(4) bond length is 2.38 Å. The Na(1)-O(6) bond length is 2.33 Å. In the second Na site, Na(2) is bonded to one O(1), one O(2), one O(3), one O(5), and one O(6) atom to form distorted NaO5 square pyramids that share  a cornercorner with one Na(1)O4 tetrahedra,  a cornercorner with one Ni(2)O4 tetrahedra,  an edgeedge with one Na(1)O4 tetrahedra, and  an edgeedge with one Ni(2)O4 tetrahedra. The Na(2)-O(1) bond length is 2.34 Å. The Na(2)-O(2) bond length is 2.47 Å. The Na(2)-O(3) bond length is 2.29 Å. The Na(2)-O(5) bond length is 2.34 Å. The Na(2)-O(6) bond length is 2.50 Å. In the third Na site, Na(3) is bonded in a 5-coordinate geometry to one O(1), one O(2), one O(4), one O(5), and one O(6) atom. The Na(3)-O(1) bond length is 2.33 Å. The Na(3)-O(2) bond length is 2.47 Å. The Na(3)-O(4) bond length is 2.41 Å. The Na(3)-O(5) bond length is 2.26 Å. The Na(3)-O(6) bond length is 2.60 Å. In the fourth Na site, Na(4) is bonded in a 4-coordinate geometry to one O(1), one O(3), one O(5), and one O(6) atom. The Na(4)-O(1) bond length is 2.40 Å. The Na(4)-O(3) bond length is 2.26 Å. The Na(4)-O(5) bond length is 2.21 Å. The Na(4)-O(6) bond length is 2.45 Å. Mg(1) is bonded in a rectangular see-saw-like geometry to one O(1), one O(3), one O(4), and one O(5) atom. The Mg(1)-O(1) bond length is 2.04 Å. The Mg(1)-O(3) bond length is 1.91 Å. The Mg(1)-O(4) bond length is 2.02 Å. The Mg(1)-O(5) bond length is 1.97 Å. There are two inequivalent Ni sites. In the first Ni site, Ni(1) is bonded in a 5-coordinate geometry to one O(1), one O(2), one O(4), one O(5), and one O(6) atom. The Ni(1)-O(1) bond length is 1.93 Å. The Ni(1)-O(2) bond length is 1.93 Å. The Ni(1)-O(4) bond length is 2.23 Å. The Ni(1)-O(5) bond length is 1.92 Å. The Ni(1)-O(6) bond length is 2.00 Å. In the second Ni site, Ni(2) is bonded to one O(2), one O(3), one O(4), and one O(6) atom to form NiO4 tetrahedra that share  a cornercorner with one Na(2)O5 square pyramid, corners with three equivalent Na(1)O4 tetrahedra, and  an edgeedge with one Na(2)O5 square pyramid. The Ni(2)-O(2) bond length is 1.90 Å. The Ni(2)-O(3) bond length is 1.84 Å. The Ni(2)-O(4) bond length is 1.91 Å. The Ni(2)-O(6) bond length is 1.88 Å. There are six 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 Mg(1), and one Ni(1) atom to form distorted ONa4MgNi octahedra that share corners with three equivalent O(3)Na2MgNi tetrahedra, corners with two equivalent O(2)Na3Ni2 trigonal bipyramids, corners with three equivalent O(5)Na3MgNi trigonal bipyramids,  an edgeedge with one O(5)Na3MgNi trigonal bipyramid, and  an edgeedge with one O(2)Na3Ni2 trigonal bipyramid. In the second O site, O(2) is bonded to one Na(1), one Na(2), one Na(3), one Ni(1), and one Ni(2) atom to form distorted ONa3Ni2 trigonal bipyramids that share corners with two equivalent O(1)Na4MgNi octahedra, corners with two equivalent O(3)Na2MgNi tetrahedra,  a cornercorner with one O(5)Na3MgNi trigonal bipyramid,  an edgeedge with one O(1)Na4MgNi octahedra, and  an edgeedge with one O(5)Na3MgNi trigonal bipyramid. The corner-sharing octahedral tilt angles range from 8-71°. In the third O site, O(3) is bonded to one Na(2), one Na(4), one Mg(1), and one Ni(2) atom to form ONa2MgNi tetrahedra that share corners with three equivalent O(1)Na4MgNi octahedra, corners with two equivalent O(2)Na3Ni2 trigonal bipyramids, and corners with three equivalent O(5)Na3MgNi trigonal bipyramids. The corner-sharing octahedral tilt angles range from 57-69°. In the fourth O site, O(4) is bonded in a 5-coordinate geometry to one Na(1), one Na(3), one Mg(1), one Ni(1), and one Ni(2) atom. In the fifth O site, O(5) is bonded to one Na(2), one Na(3), one Na(4), one Mg(1), and one Ni(1) atom to form distorted ONa3MgNi trigonal bipyramids that share corners with three equivalent O(1)Na4MgNi octahedra, corners with three equivalent O(3)Na2MgNi tetrahedra,  a cornercorner with one O(2)Na3Ni2 trigonal bipyramid,  an edgeedge with one O(1)Na4MgNi octahedra, and  an edgeedge with one O(2)Na3Ni2 trigonal bipyramid. The corner-sharing octahedral tilt angles range from 17-64°. In the sixth O site, O(6) is bonded in a 6-coordinate geometry to one Na(1), one Na(2), one Na(3), one Na(4), one Ni(1), and one Ni(2) atom.