Na3(NiO2)2 crystallizes in the orthorhombic Pnma space group. There are two inequivalent Na sites. In the first Na site, Na(1) is bonded in a 6-coordinate geometry to one O(3), two equivalent O(1), and three equivalent O(2) atoms. In the second Na site, Na(2) is bonded in a 4-coordinate geometry to two equivalent O(2) and two equivalent O(3) atoms. Ni(1) is bonded to one O(1), one O(3), and two equivalent O(2) atoms to form distorted edge-sharing NiO4 tetrahedra. There are three inequivalent O sites. In the first O site, O(1) is bonded in a 6-coordinate geometry to four equivalent Na(1) and two equivalent Ni(1) atoms. In the second O site, O(2) is bonded to one Na(2), three equivalent Na(1), and two equivalent Ni(1) atoms to form a mixture of distorted corner and edge-sharing ONa4Ni2 octahedra. The corner-sharing octahedral tilt angles range from 52-84°. In the third O site, O(3) is bonded in a 6-coordinate geometry to two equivalent Na(1), two equivalent Na(2), and two equivalent Ni(1) atoms.
Na3(NiO2)2 crystallizes in the orthorhombic Pnma space group. There are two inequivalent Na sites. In the first Na site, Na(1) is bonded in a 6-coordinate geometry to one O(3), two equivalent O(1), and three equivalent O(2) atoms. The Na(1)-O(3) bond length is 2.85 Å. There is one shorter (2.42 Å) and one longer (2.54 Å) Na(1)-O(1) bond length. There are a spread of Na(1)-O(2) bond distances ranging from 2.44-2.68 Å. In the second Na site, Na(2) is bonded in a 4-coordinate geometry to two equivalent O(2) and two equivalent O(3) atoms. Both Na(2)-O(2) bond lengths are 2.43 Å. There is one shorter (2.28 Å) and one longer (2.35 Å) Na(2)-O(3) bond length. Ni(1) is bonded to one O(1), one O(3), and two equivalent O(2) atoms to form distorted edge-sharing NiO4 tetrahedra. The Ni(1)-O(1) bond length is 1.93 Å. The Ni(1)-O(3) bond length is 1.89 Å. There is one shorter (1.90 Å) and one longer (1.94 Å) Ni(1)-O(2) bond length. There are three inequivalent O sites. In the first O site, O(1) is bonded in a 6-coordinate geometry to four equivalent Na(1) and two equivalent Ni(1) atoms. In the second O site, O(2) is bonded to one Na(2), three equivalent Na(1), and two equivalent Ni(1) atoms to form a mixture of distorted corner and edge-sharing ONa4Ni2 octahedra. The corner-sharing octahedral tilt angles range from 52-84°. In the third O site, O(3) is bonded in a 6-coordinate geometry to two equivalent Na(1), two equivalent Na(2), and two equivalent Ni(1) atoms.