Na6NiO4 is alpha Pu-derived structured and crystallizes in the monoclinic Cc space group. There are six inequivalent Na sites. In the first Na site, Na(1) is bonded in a 4-coordinate geometry to one O(3), one O(4), and two equivalent O(1) atoms. In the second Na site, Na(2) is bonded in a 3-coordinate geometry to one O(3), two equivalent O(1), and two equivalent O(2) atoms. In the third Na site, Na(3) is bonded to one O(3), one O(4), and two equivalent O(2) atoms to form distorted NaO4 trigonal pyramids that share corners with two equivalent Ni(1)O4 tetrahedra, corners with two equivalent Na(3)O4 trigonal pyramids, corners with four equivalent Na(6)O4 trigonal pyramids, and  an edgeedge with one Ni(1)O4 tetrahedra. In the fourth Na site, Na(4) is bonded in a 5-coordinate geometry to one O(1), one O(2), one O(3), and two equivalent O(4) atoms. In the fifth Na site, Na(5) is bonded in a 3-coordinate geometry to one O(1), one O(2), one O(3), and two equivalent O(4) atoms. In the sixth Na site, Na(6) is bonded to one O(1), one O(2), one O(3), and one O(4) atom to form distorted NaO4 trigonal pyramids that share corners with two equivalent Ni(1)O4 tetrahedra, corners with four equivalent Na(3)O4 trigonal pyramids, and  an edgeedge with one Ni(1)O4 tetrahedra. Ni(1) is bonded to one O(1), one O(2), one O(3), and one O(4) atom to form NiO4 tetrahedra that share corners with two equivalent Na(3)O4 trigonal pyramids, corners with two equivalent Na(6)O4 trigonal pyramids,  an edgeedge with one Na(3)O4 trigonal pyramid, and  an edgeedge with one Na(6)O4 trigonal pyramid. There are four inequivalent O sites. In the first O site, O(1) is bonded in a 8-coordinate geometry to one Na(4), one Na(5), one Na(6), two equivalent Na(1), two equivalent Na(2), and one Ni(1) atom. In the second O site, O(2) is bonded in a 8-coordinate geometry to one Na(4), one Na(5), one Na(6), two equivalent Na(2), two equivalent Na(3), and one Ni(1) 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 Ni(1) atom. In the fourth O site, O(4) is bonded in a 8-coordinate geometry to one Na(1), one Na(3), one Na(6), two equivalent Na(4), two equivalent Na(5), and one Ni(1) atom.
Na6NiO4 is alpha Pu-derived structured and crystallizes in the monoclinic Cc space group. There are six inequivalent Na sites. In the first Na site, Na(1) is bonded in a 4-coordinate geometry to one O(3), one O(4), and two equivalent O(1) atoms. The Na(1)-O(3) bond length is 2.56 Å. The Na(1)-O(4) bond length is 2.29 Å. There is one shorter (2.27 Å) and one longer (2.34 Å) Na(1)-O(1) bond length. In the second Na site, Na(2) is bonded in a 3-coordinate geometry to one O(3), two equivalent O(1), and two equivalent O(2) atoms. The Na(2)-O(3) bond length is 2.32 Å. There is one shorter (2.43 Å) and one longer (2.69 Å) Na(2)-O(1) bond length. There is one shorter (2.43 Å) and one longer (2.67 Å) Na(2)-O(2) bond length. In the third Na site, Na(3) is bonded to one O(3), one O(4), and two equivalent O(2) atoms to form distorted NaO4 trigonal pyramids that share corners with two equivalent Ni(1)O4 tetrahedra, corners with two equivalent Na(3)O4 trigonal pyramids, corners with four equivalent Na(6)O4 trigonal pyramids, and  an edgeedge with one Ni(1)O4 tetrahedra. The Na(3)-O(3) bond length is 2.49 Å. The Na(3)-O(4) bond length is 2.33 Å. Both Na(3)-O(2) bond lengths are 2.33 Å. In the fourth Na site, Na(4) is bonded in a 5-coordinate geometry to one O(1), one O(2), one O(3), and two equivalent O(4) atoms. The Na(4)-O(1) bond length is 2.47 Å. The Na(4)-O(2) bond length is 2.61 Å. The Na(4)-O(3) bond length is 2.36 Å. There is one shorter (2.46 Å) and one longer (2.59 Å) Na(4)-O(4) bond length. In the fifth Na site, Na(5) is bonded in a 3-coordinate geometry to one O(1), one O(2), one O(3), and two equivalent O(4) atoms. The Na(5)-O(1) bond length is 2.74 Å. The Na(5)-O(2) bond length is 2.39 Å. The Na(5)-O(3) bond length is 2.30 Å. There is one shorter (2.37 Å) and one longer (2.71 Å) Na(5)-O(4) bond length. In the sixth Na site, Na(6) is bonded to one O(1), one O(2), one O(3), and one O(4) atom to form distorted NaO4 trigonal pyramids that share corners with two equivalent Ni(1)O4 tetrahedra, corners with four equivalent Na(3)O4 trigonal pyramids, and  an edgeedge with one Ni(1)O4 tetrahedra. The Na(6)-O(1) bond length is 2.29 Å. The Na(6)-O(2) bond length is 2.31 Å. The Na(6)-O(3) bond length is 2.46 Å. The Na(6)-O(4) bond length is 2.31 Å. Ni(1) is bonded to one O(1), one O(2), one O(3), and one O(4) atom to form NiO4 tetrahedra that share corners with two equivalent Na(3)O4 trigonal pyramids, corners with two equivalent Na(6)O4 trigonal pyramids,  an edgeedge with one Na(3)O4 trigonal pyramid, and  an edgeedge with one Na(6)O4 trigonal pyramid. The Ni(1)-O(1) bond length is 1.96 Å. The Ni(1)-O(2) bond length is 2.00 Å. The Ni(1)-O(3) bond length is 1.97 Å. The Ni(1)-O(4) bond length is 1.99 Å. There are four inequivalent O sites. In the first O site, O(1) is bonded in a 8-coordinate geometry to one Na(4), one Na(5), one Na(6), two equivalent Na(1), two equivalent Na(2), and one Ni(1) atom. In the second O site, O(2) is bonded in a 8-coordinate geometry to one Na(4), one Na(5), one Na(6), two equivalent Na(2), two equivalent Na(3), and one Ni(1) 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 Ni(1) atom. In the fourth O site, O(4) is bonded in a 8-coordinate geometry to one Na(1), one Na(3), one Na(6), two equivalent Na(4), two equivalent Na(5), and one Ni(1) atom.