Na4Mg(NiO2)5 crystallizes in the triclinic P1 space group. There are four inequivalent Na sites. In the first Na site, Na(1) is bonded in a 6-coordinate geometry to one O(10), one O(2), one O(3), one O(5), one O(6), and one O(8) atom. In the second Na site, Na(2) is bonded in a 5-coordinate geometry to one O(1), one O(3), one O(4), one O(5), and one O(7) atom. In the third Na site, Na(3) is bonded in a 5-coordinate geometry to one O(10), one O(4), one O(6), one O(7), and one O(8) atom. In the fourth Na site, Na(4) is bonded in a 5-coordinate geometry to one O(1), one O(5), one O(6), one O(8), and one O(9) atom. Mg(1) is bonded in a 4-coordinate geometry to one O(3), one O(6), one O(7), and one O(9) atom. There are five inequivalent Ni sites. In the first Ni site, Ni(1) is bonded in a 5-coordinate geometry to one O(1), one O(10), one O(4), one O(6), and one O(8) atom. In the second Ni site, Ni(2) is bonded to one O(10), one O(2), one O(4), one O(5), and one O(9) atom to form edge-sharing NiO5 square pyramids. In the third Ni site, Ni(3) is bonded to one O(1), one O(2), one O(3), one O(6), and one O(9) atom to form distorted edge-sharing NiO5 square pyramids. In the fourth Ni site, Ni(4) is bonded to one O(1), one O(10), one O(3), one O(5), and one O(7) atom to form distorted edge-sharing NiO5 trigonal bipyramids. In the fifth Ni site, Ni(5) is bonded in a 5-coordinate geometry to one O(2), one O(3), one O(4), one O(7), and one O(8) atom. There are ten inequivalent O sites. In the first O site, O(1) is bonded to one Na(2), one Na(4), one Ni(1), one Ni(3), and one Ni(4) atom to form distorted ONa2Ni3 square pyramids that share  a cornercorner with one O(3)Na2MgNi3 octahedra,  a cornercorner with one O(6)Na3MgNi2 octahedra, corners with two equivalent O(4)Na2Ni3 trigonal bipyramids, corners with two equivalent O(9)NaMgNi2 trigonal pyramids,  an edgeedge with one O(3)Na2MgNi3 octahedra, and  an edgeedge with one O(6)Na3MgNi2 octahedra. The corner-sharing octahedral tilt angles range from 25-66°. In the second O site, O(2) is bonded in a rectangular see-saw-like geometry to one Na(1), one Ni(2), one Ni(3), and one Ni(5) atom. In the third O site, O(3) is bonded to one Na(1), one Na(2), one Mg(1), one Ni(3), one Ni(4), and one Ni(5) atom to form distorted ONa2MgNi3 octahedra that share  a cornercorner with one O(6)Na3MgNi2 octahedra,  a cornercorner with one O(1)Na2Ni3 square pyramid, corners with two equivalent O(9)NaMgNi2 trigonal pyramids,  an edgeedge with one O(6)Na3MgNi2 octahedra,  an edgeedge with one O(1)Na2Ni3 square pyramid, and  an edgeedge with one O(4)Na2Ni3 trigonal bipyramid. The corner-sharing octahedral tilt angles are 53°. In the fourth O site, O(4) is bonded to one Na(2), one Na(3), one Ni(1), one Ni(2), and one Ni(5) atom to form ONa2Ni3 trigonal bipyramids that share corners with two equivalent O(1)Na2Ni3 square pyramids,  a cornercorner with one O(9)NaMgNi2 trigonal pyramid,  an edgeedge with one O(3)Na2MgNi3 octahedra, and  an edgeedge with one O(6)Na3MgNi2 octahedra. In the fifth O site, O(5) is bonded in a 5-coordinate geometry to one Na(1), one Na(2), one Na(4), one Ni(2), and one Ni(4) atom. In the sixth O site, O(6) is bonded to one Na(1), one Na(3), one Na(4), one Mg(1), one Ni(1), and one Ni(3) atom to form distorted ONa3MgNi2 octahedra that share  a cornercorner with one O(3)Na2MgNi3 octahedra,  a cornercorner with one O(1)Na2Ni3 square pyramid,  an edgeedge with one O(3)Na2MgNi3 octahedra,  an edgeedge with one O(1)Na2Ni3 square pyramid,  an edgeedge with one O(4)Na2Ni3 trigonal bipyramid, and  a faceface with one O(9)NaMgNi2 trigonal pyramid. The corner-sharing octahedral tilt angles are 53°. In the seventh O site, O(7) is bonded in a 5-coordinate geometry to one Na(2), one Na(3), one Mg(1), one Ni(4), and one Ni(5) atom. In the eighth O site, O(8) is bonded in a 5-coordinate geometry to one Na(1), one Na(3), one Na(4), one Ni(1), and one Ni(5) atom. In the ninth O site, O(9) is bonded to one Na(4), one Mg(1), one Ni(2), and one Ni(3) atom to form distorted ONaMgNi2 trigonal pyramids that share corners with two equivalent O(3)Na2MgNi3 octahedra, corners with two equivalent O(1)Na2Ni3 square pyramids,  a cornercorner with one O(4)Na2Ni3 trigonal bipyramid, and  a faceface with one O(6)Na3MgNi2 octahedra. The corner-sharing octahedral tilt angles range from 40-77°. In the tenth O site, O(10) is bonded in a 5-coordinate geometry to one Na(1), one Na(3), one Ni(1), one Ni(2), and one Ni(4) atom.
Na4Mg(NiO2)5 crystallizes in the triclinic P1 space group. There are four inequivalent Na sites. In the first Na site, Na(1) is bonded in a 6-coordinate geometry to one O(10), one O(2), one O(3), one O(5), one O(6), and one O(8) atom. The Na(1)-O(10) bond length is 2.30 Å. The Na(1)-O(2) bond length is 2.25 Å. The Na(1)-O(3) bond length is 2.34 Å. The Na(1)-O(5) bond length is 2.54 Å. The Na(1)-O(6) bond length is 2.64 Å. The Na(1)-O(8) bond length is 2.66 Å. In the second Na site, Na(2) is bonded in a 5-coordinate geometry to one O(1), one O(3), one O(4), one O(5), and one O(7) atom. The Na(2)-O(1) bond length is 2.69 Å. The Na(2)-O(3) bond length is 2.46 Å. The Na(2)-O(4) bond length is 2.47 Å. The Na(2)-O(5) bond length is 2.44 Å. The Na(2)-O(7) bond length is 2.37 Å. In the third Na site, Na(3) is bonded in a 5-coordinate geometry to one O(10), one O(4), one O(6), one O(7), and one O(8) atom. The Na(3)-O(10) bond length is 2.91 Å. The Na(3)-O(4) bond length is 2.29 Å. The Na(3)-O(6) bond length is 2.39 Å. The Na(3)-O(7) bond length is 2.34 Å. The Na(3)-O(8) bond length is 2.38 Å. In the fourth Na site, Na(4) is bonded in a 5-coordinate geometry to one O(1), one O(5), one O(6), one O(8), and one O(9) atom. The Na(4)-O(1) bond length is 2.27 Å. The Na(4)-O(5) bond length is 2.22 Å. The Na(4)-O(6) bond length is 2.48 Å. The Na(4)-O(8) bond length is 2.28 Å. The Na(4)-O(9) bond length is 2.34 Å. Mg(1) is bonded in a 4-coordinate geometry to one O(3), one O(6), one O(7), and one O(9) atom. The Mg(1)-O(3) bond length is 1.97 Å. The Mg(1)-O(6) bond length is 2.05 Å. The Mg(1)-O(7) bond length is 1.99 Å. The Mg(1)-O(9) bond length is 1.96 Å. There are five inequivalent Ni sites. In the first Ni site, Ni(1) is bonded in a 5-coordinate geometry to one O(1), one O(10), one O(4), one O(6), and one O(8) atom. The Ni(1)-O(1) bond length is 1.91 Å. The Ni(1)-O(10) bond length is 2.45 Å. The Ni(1)-O(4) bond length is 1.88 Å. The Ni(1)-O(6) bond length is 1.98 Å. The Ni(1)-O(8) bond length is 1.90 Å. In the second Ni site, Ni(2) is bonded to one O(10), one O(2), one O(4), one O(5), and one O(9) atom to form edge-sharing NiO5 square pyramids. The Ni(2)-O(10) bond length is 1.88 Å. The Ni(2)-O(2) bond length is 1.91 Å. The Ni(2)-O(4) bond length is 2.14 Å. The Ni(2)-O(5) bond length is 1.90 Å. The Ni(2)-O(9) bond length is 1.91 Å. In the third Ni site, Ni(3) is bonded to one O(1), one O(2), one O(3), one O(6), and one O(9) atom to form distorted edge-sharing NiO5 square pyramids. The Ni(3)-O(1) bond length is 1.87 Å. The Ni(3)-O(2) bond length is 1.86 Å. The Ni(3)-O(3) bond length is 2.11 Å. The Ni(3)-O(6) bond length is 1.94 Å. The Ni(3)-O(9) bond length is 1.91 Å. In the fourth Ni site, Ni(4) is bonded to one O(1), one O(10), one O(3), one O(5), and one O(7) atom to form distorted edge-sharing NiO5 trigonal bipyramids. The Ni(4)-O(1) bond length is 2.07 Å. The Ni(4)-O(10) bond length is 1.87 Å. The Ni(4)-O(3) bond length is 2.00 Å. The Ni(4)-O(5) bond length is 1.87 Å. The Ni(4)-O(7) bond length is 1.94 Å. In the fifth Ni site, Ni(5) is bonded in a 5-coordinate geometry to one O(2), one O(3), one O(4), one O(7), and one O(8) atom. The Ni(5)-O(2) bond length is 1.97 Å. The Ni(5)-O(3) bond length is 2.23 Å. The Ni(5)-O(4) bond length is 2.02 Å. The Ni(5)-O(7) bond length is 2.09 Å. The Ni(5)-O(8) bond length is 1.94 Å. There are ten inequivalent O sites. In the first O site, O(1) is bonded to one Na(2), one Na(4), one Ni(1), one Ni(3), and one Ni(4) atom to form distorted ONa2Ni3 square pyramids that share  a cornercorner with one O(3)Na2MgNi3 octahedra,  a cornercorner with one O(6)Na3MgNi2 octahedra, corners with two equivalent O(4)Na2Ni3 trigonal bipyramids, corners with two equivalent O(9)NaMgNi2 trigonal pyramids,  an edgeedge with one O(3)Na2MgNi3 octahedra, and  an edgeedge with one O(6)Na3MgNi2 octahedra. The corner-sharing octahedral tilt angles range from 25-66°. In the second O site, O(2) is bonded in a rectangular see-saw-like geometry to one Na(1), one Ni(2), one Ni(3), and one Ni(5) atom. In the third O site, O(3) is bonded to one Na(1), one Na(2), one Mg(1), one Ni(3), one Ni(4), and one Ni(5) atom to form distorted ONa2MgNi3 octahedra that share  a cornercorner with one O(6)Na3MgNi2 octahedra,  a cornercorner with one O(1)Na2Ni3 square pyramid, corners with two equivalent O(9)NaMgNi2 trigonal pyramids,  an edgeedge with one O(6)Na3MgNi2 octahedra,  an edgeedge with one O(1)Na2Ni3 square pyramid, and  an edgeedge with one O(4)Na2Ni3 trigonal bipyramid. The corner-sharing octahedral tilt angles are 53°. In the fourth O site, O(4) is bonded to one Na(2), one Na(3), one Ni(1), one Ni(2), and one Ni(5) atom to form ONa2Ni3 trigonal bipyramids that share corners with two equivalent O(1)Na2Ni3 square pyramids,  a cornercorner with one O(9)NaMgNi2 trigonal pyramid,  an edgeedge with one O(3)Na2MgNi3 octahedra, and  an edgeedge with one O(6)Na3MgNi2 octahedra. In the fifth O site, O(5) is bonded in a 5-coordinate geometry to one Na(1), one Na(2), one Na(4), one Ni(2), and one Ni(4) atom. In the sixth O site, O(6) is bonded to one Na(1), one Na(3), one Na(4), one Mg(1), one Ni(1), and one Ni(3) atom to form distorted ONa3MgNi2 octahedra that share  a cornercorner with one O(3)Na2MgNi3 octahedra,  a cornercorner with one O(1)Na2Ni3 square pyramid,  an edgeedge with one O(3)Na2MgNi3 octahedra,  an edgeedge with one O(1)Na2Ni3 square pyramid,  an edgeedge with one O(4)Na2Ni3 trigonal bipyramid, and  a faceface with one O(9)NaMgNi2 trigonal pyramid. The corner-sharing octahedral tilt angles are 53°. In the seventh O site, O(7) is bonded in a 5-coordinate geometry to one Na(2), one Na(3), one Mg(1), one Ni(4), and one Ni(5) atom. In the eighth O site, O(8) is bonded in a 5-coordinate geometry to one Na(1), one Na(3), one Na(4), one Ni(1), and one Ni(5) atom. In the ninth O site, O(9) is bonded to one Na(4), one Mg(1), one Ni(2), and one Ni(3) atom to form distorted ONaMgNi2 trigonal pyramids that share corners with two equivalent O(3)Na2MgNi3 octahedra, corners with two equivalent O(1)Na2Ni3 square pyramids,  a cornercorner with one O(4)Na2Ni3 trigonal bipyramid, and  a faceface with one O(6)Na3MgNi2 octahedra. The corner-sharing octahedral tilt angles range from 40-77°. In the tenth O site, O(10) is bonded in a 5-coordinate geometry to one Na(1), one Na(3), one Ni(1), one Ni(2), and one Ni(4) atom.