Na3NiO3 crystallizes in the triclinic P-1 space group. There are three inequivalent Na sites. In the first Na site, Na(1) is bonded to one O(1), two equivalent O(2), and two equivalent O(3) atoms to form distorted NaO5 trigonal bipyramids that share corners with two equivalent Na(2)O4 trigonal pyramids, corners with three equivalent Ni(1)O4 trigonal pyramids, edges with two equivalent Na(1)O5 trigonal bipyramids, edges with two equivalent Na(2)O4 trigonal pyramids, and edges with two equivalent Ni(1)O4 trigonal pyramids. In the second Na site, Na(2) is bonded to one O(2), one O(3), and two equivalent O(1) atoms to form NaO4 trigonal pyramids that share corners with two equivalent Na(1)O5 trigonal bipyramids, corners with five equivalent Ni(1)O4 trigonal pyramids, edges with two equivalent Na(1)O5 trigonal bipyramids, and  an edgeedge with one Na(2)O4 trigonal pyramid. In the third Na site, Na(3) is bonded in a 5-coordinate geometry to one O(3), two equivalent O(1), and two equivalent O(2) atoms. Ni(1) is bonded to one O(1), one O(2), and two equivalent O(3) atoms to form distorted NiO4 trigonal pyramids that share corners with three equivalent Na(1)O5 trigonal bipyramids, corners with five equivalent Na(2)O4 trigonal pyramids, edges with two equivalent Na(1)O5 trigonal bipyramids, and  an edgeedge with one Ni(1)O4 trigonal pyramid. There are three inequivalent O sites. In the first O site, O(1) is bonded in a 6-coordinate geometry to one Na(1), two equivalent Na(2), two equivalent Na(3), and one Ni(1) atom. In the second O site, O(2) is bonded to one Na(2), two equivalent Na(1), two equivalent Na(3), and one Ni(1) atom to form distorted edge-sharing ONa5Ni octahedra. In the third O site, O(3) is bonded in a 6-coordinate geometry to one Na(2), one Na(3), two equivalent Na(1), and two equivalent Ni(1) atoms.
Na3NiO3 crystallizes in the triclinic P-1 space group. There are three inequivalent Na sites. In the first Na site, Na(1) is bonded to one O(1), two equivalent O(2), and two equivalent O(3) atoms to form distorted NaO5 trigonal bipyramids that share corners with two equivalent Na(2)O4 trigonal pyramids, corners with three equivalent Ni(1)O4 trigonal pyramids, edges with two equivalent Na(1)O5 trigonal bipyramids, edges with two equivalent Na(2)O4 trigonal pyramids, and edges with two equivalent Ni(1)O4 trigonal pyramids. The Na(1)-O(1) bond length is 2.45 Å. There is one shorter (2.30 Å) and one longer (2.35 Å) Na(1)-O(2) bond length. There is one shorter (2.28 Å) and one longer (2.56 Å) Na(1)-O(3) bond length. In the second Na site, Na(2) is bonded to one O(2), one O(3), and two equivalent O(1) atoms to form NaO4 trigonal pyramids that share corners with two equivalent Na(1)O5 trigonal bipyramids, corners with five equivalent Ni(1)O4 trigonal pyramids, edges with two equivalent Na(1)O5 trigonal bipyramids, and  an edgeedge with one Na(2)O4 trigonal pyramid. The Na(2)-O(2) bond length is 2.26 Å. The Na(2)-O(3) bond length is 2.24 Å. There is one shorter (2.26 Å) and one longer (2.43 Å) Na(2)-O(1) bond length. In the third Na site, Na(3) is bonded in a 5-coordinate geometry to one O(3), two equivalent O(1), and two equivalent O(2) atoms. The Na(3)-O(3) bond length is 2.53 Å. There is one shorter (2.33 Å) and one longer (2.53 Å) Na(3)-O(1) bond length. There is one shorter (2.34 Å) and one longer (2.46 Å) Na(3)-O(2) bond length. Ni(1) is bonded to one O(1), one O(2), and two equivalent O(3) atoms to form distorted NiO4 trigonal pyramids that share corners with three equivalent Na(1)O5 trigonal bipyramids, corners with five equivalent Na(2)O4 trigonal pyramids, edges with two equivalent Na(1)O5 trigonal bipyramids, and  an edgeedge with one Ni(1)O4 trigonal pyramid. The Ni(1)-O(1) bond length is 1.81 Å. The Ni(1)-O(2) bond length is 1.82 Å. There is one shorter (1.88 Å) and one longer (1.98 Å) Ni(1)-O(3) bond length. There are three inequivalent O sites. In the first O site, O(1) is bonded in a 6-coordinate geometry to one Na(1), two equivalent Na(2), two equivalent Na(3), and one Ni(1) atom. In the second O site, O(2) is bonded to one Na(2), two equivalent Na(1), two equivalent Na(3), and one Ni(1) atom to form distorted edge-sharing ONa5Ni octahedra. In the third O site, O(3) is bonded in a 6-coordinate geometry to one Na(2), one Na(3), two equivalent Na(1), and two equivalent Ni(1) atoms.