Na3MnO3 crystallizes in the monoclinic P2_1/c space group. There are three inequivalent Na sites. In the first Na site, Na(1) is bonded in a 5-coordinate geometry to one O(2), two equivalent O(1), and two equivalent O(3) atoms. In the second Na site, Na(2) is bonded in a 5-coordinate geometry to one O(1), two equivalent O(2), and two equivalent O(3) atoms. In the third Na site, Na(3) is bonded in a 5-coordinate geometry to one O(1), two equivalent O(2), and two equivalent O(3) atoms. Mn(1) is bonded in a distorted square co-planar geometry to one O(2), one O(3), and two equivalent O(1) atoms. There are three inequivalent O sites. In the first O site, O(1) is bonded in a 6-coordinate geometry to one Na(2), one Na(3), two equivalent Na(1), and two equivalent Mn(1) atoms. In the second O site, O(2) is bonded to one Na(1), two equivalent Na(2), two equivalent Na(3), and one Mn(1) atom to form distorted ONa5Mn octahedra that share corners with two equivalent O(2)Na5Mn octahedra, corners with three equivalent O(3)Na6Mn pentagonal bipyramids,  an edgeedge with one O(2)Na5Mn octahedra,  an edgeedge with one O(3)Na6Mn pentagonal bipyramid, and faces with two equivalent O(3)Na6Mn pentagonal bipyramids. The corner-sharing octahedral tilt angles are 67°. In the third O site, O(3) is bonded to two equivalent Na(1), two equivalent Na(2), two equivalent Na(3), and one Mn(1) atom to form distorted ONa6Mn pentagonal bipyramids that share corners with three equivalent O(2)Na5Mn octahedra,  an edgeedge with one O(2)Na5Mn octahedra, edges with three equivalent O(3)Na6Mn pentagonal bipyramids, and faces with two equivalent O(2)Na5Mn octahedra. The corner-sharing octahedral tilt angles range from 47-60°.
Na3MnO3 crystallizes in the monoclinic P2_1/c space group. There are three inequivalent Na sites. In the first Na site, Na(1) is bonded in a 5-coordinate geometry to one O(2), two equivalent O(1), and two equivalent O(3) atoms. The Na(1)-O(2) bond length is 2.38 Å. Both Na(1)-O(1) bond lengths are 2.40 Å. There is one shorter (2.53 Å) and one longer (2.63 Å) Na(1)-O(3) bond length. In the second Na site, Na(2) is bonded in a 5-coordinate geometry to one O(1), two equivalent O(2), and two equivalent O(3) atoms. The Na(2)-O(1) bond length is 2.31 Å. There is one shorter (2.44 Å) and one longer (2.58 Å) Na(2)-O(2) bond length. There is one shorter (2.49 Å) and one longer (2.50 Å) Na(2)-O(3) bond length. In the third Na site, Na(3) is bonded in a 5-coordinate geometry to one O(1), two equivalent O(2), and two equivalent O(3) atoms. The Na(3)-O(1) bond length is 2.81 Å. There is one shorter (2.37 Å) and one longer (2.39 Å) Na(3)-O(2) bond length. There is one shorter (2.28 Å) and one longer (2.47 Å) Na(3)-O(3) bond length. Mn(1) is bonded in a distorted square co-planar geometry to one O(2), one O(3), and two equivalent O(1) atoms. The Mn(1)-O(2) bond length is 1.88 Å. The Mn(1)-O(3) bond length is 1.87 Å. Both Mn(1)-O(1) bond lengths are 1.96 Å. There are three inequivalent O sites. In the first O site, O(1) is bonded in a 6-coordinate geometry to one Na(2), one Na(3), two equivalent Na(1), and two equivalent Mn(1) atoms. In the second O site, O(2) is bonded to one Na(1), two equivalent Na(2), two equivalent Na(3), and one Mn(1) atom to form distorted ONa5Mn octahedra that share corners with two equivalent O(2)Na5Mn octahedra, corners with three equivalent O(3)Na6Mn pentagonal bipyramids,  an edgeedge with one O(2)Na5Mn octahedra,  an edgeedge with one O(3)Na6Mn pentagonal bipyramid, and faces with two equivalent O(3)Na6Mn pentagonal bipyramids. The corner-sharing octahedral tilt angles are 67°. In the third O site, O(3) is bonded to two equivalent Na(1), two equivalent Na(2), two equivalent Na(3), and one Mn(1) atom to form distorted ONa6Mn pentagonal bipyramids that share corners with three equivalent O(2)Na5Mn octahedra,  an edgeedge with one O(2)Na5Mn octahedra, edges with three equivalent O(3)Na6Mn pentagonal bipyramids, and faces with two equivalent O(2)Na5Mn octahedra. The corner-sharing octahedral tilt angles range from 47-60°.