Na3MnO4 crystallizes in the orthorhombic Pnma space group. There are two inequivalent Na sites. In the first Na site, Na(1) is bonded to one O(1), one O(3), and two equivalent O(2) atoms to form NaO4 tetrahedra that share corners with four equivalent Na(1)O4 tetrahedra, corners with four equivalent Mn(1)O4 tetrahedra, corners with two equivalent Na(2)O4 trigonal pyramids, and  an edgeedge with one Na(2)O4 trigonal pyramid. In the second Na site, Na(2) is bonded to one O(1), one O(3), and two equivalent O(2) atoms to form NaO4 trigonal pyramids that share corners with four equivalent Na(1)O4 tetrahedra, corners with four equivalent Mn(1)O4 tetrahedra, and edges with two equivalent Na(1)O4 tetrahedra. Mn(1) is bonded to one O(1), one O(3), and two equivalent O(2) atoms to form MnO4 tetrahedra that share corners with eight equivalent Na(1)O4 tetrahedra and corners with four equivalent Na(2)O4 trigonal pyramids. There are three inequivalent O sites. In the first O site, O(1) is bonded to one Na(2), two equivalent Na(1), and one Mn(1) atom to form corner-sharing ONa3Mn tetrahedra. In the second O site, O(2) is bonded to one Na(2), two equivalent Na(1), and one Mn(1) atom to form a mixture of distorted corner and edge-sharing ONa3Mn trigonal pyramids. In the third O site, O(3) is bonded to one Na(2), two equivalent Na(1), and one Mn(1) atom to form a mixture of distorted corner and edge-sharing ONa3Mn trigonal pyramids.
Na3MnO4 crystallizes in the orthorhombic Pnma space group. There are two inequivalent Na sites. In the first Na site, Na(1) is bonded to one O(1), one O(3), and two equivalent O(2) atoms to form NaO4 tetrahedra that share corners with four equivalent Na(1)O4 tetrahedra, corners with four equivalent Mn(1)O4 tetrahedra, corners with two equivalent Na(2)O4 trigonal pyramids, and  an edgeedge with one Na(2)O4 trigonal pyramid. The Na(1)-O(1) bond length is 2.21 Å. The Na(1)-O(3) bond length is 2.26 Å. There is one shorter (2.27 Å) and one longer (2.31 Å) Na(1)-O(2) bond length. In the second Na site, Na(2) is bonded to one O(1), one O(3), and two equivalent O(2) atoms to form NaO4 trigonal pyramids that share corners with four equivalent Na(1)O4 tetrahedra, corners with four equivalent Mn(1)O4 tetrahedra, and edges with two equivalent Na(1)O4 tetrahedra. The Na(2)-O(1) bond length is 2.22 Å. The Na(2)-O(3) bond length is 2.37 Å. Both Na(2)-O(2) bond lengths are 2.34 Å. Mn(1) is bonded to one O(1), one O(3), and two equivalent O(2) atoms to form MnO4 tetrahedra that share corners with eight equivalent Na(1)O4 tetrahedra and corners with four equivalent Na(2)O4 trigonal pyramids. The Mn(1)-O(1) bond length is 1.69 Å. The Mn(1)-O(3) bond length is 1.70 Å. Both Mn(1)-O(2) bond lengths are 1.70 Å. There are three inequivalent O sites. In the first O site, O(1) is bonded to one Na(2), two equivalent Na(1), and one Mn(1) atom to form corner-sharing ONa3Mn tetrahedra. In the second O site, O(2) is bonded to one Na(2), two equivalent Na(1), and one Mn(1) atom to form a mixture of distorted corner and edge-sharing ONa3Mn trigonal pyramids. In the third O site, O(3) is bonded to one Na(2), two equivalent Na(1), and one Mn(1) atom to form a mixture of distorted corner and edge-sharing ONa3Mn trigonal pyramids.