NaMnO2 crystallizes in the orthorhombic Pnma space group. Na(1) is bonded to three equivalent O(1) and three equivalent O(2) atoms to form NaO6 octahedra that share corners with four equivalent Na(1)O6 octahedra, corners with ten equivalent Mn(1)O5 square pyramids, edges with four equivalent Na(1)O6 octahedra,  an edgeedge with one Mn(1)O5 square pyramid, and  a faceface with one Mn(1)O5 square pyramid. The corner-sharing octahedral tilt angles are 53°. Mn(1) is bonded to two equivalent O(1) and three equivalent O(2) atoms to form distorted MnO5 square pyramids that share corners with ten equivalent Na(1)O6 octahedra,  an edgeedge with one Na(1)O6 octahedra, edges with four equivalent Mn(1)O5 square pyramids, and  a faceface with one Na(1)O6 octahedra. The corner-sharing octahedral tilt angles range from 45-82°. There are two inequivalent O sites. In the first O site, O(1) is bonded in a 5-coordinate geometry to three equivalent Na(1) and two equivalent Mn(1) atoms. In the second O site, O(2) is bonded in a 6-coordinate geometry to three equivalent Na(1) and three equivalent Mn(1) atoms.
NaMnO2 crystallizes in the orthorhombic Pnma space group. Na(1) is bonded to three equivalent O(1) and three equivalent O(2) atoms to form NaO6 octahedra that share corners with four equivalent Na(1)O6 octahedra, corners with ten equivalent Mn(1)O5 square pyramids, edges with four equivalent Na(1)O6 octahedra,  an edgeedge with one Mn(1)O5 square pyramid, and  a faceface with one Mn(1)O5 square pyramid. The corner-sharing octahedral tilt angles are 53°. There is one shorter (2.37 Å) and two longer (2.43 Å) Na(1)-O(1) bond lengths. There are two shorter (2.46 Å) and one longer (2.50 Å) Na(1)-O(2) bond length. Mn(1) is bonded to two equivalent O(1) and three equivalent O(2) atoms to form distorted MnO5 square pyramids that share corners with ten equivalent Na(1)O6 octahedra,  an edgeedge with one Na(1)O6 octahedra, edges with four equivalent Mn(1)O5 square pyramids, and  a faceface with one Na(1)O6 octahedra. The corner-sharing octahedral tilt angles range from 45-82°. Both Mn(1)-O(1) bond lengths are 1.95 Å. There are two shorter (1.97 Å) and one longer (2.41 Å) Mn(1)-O(2) bond length. There are two inequivalent O sites. In the first O site, O(1) is bonded in a 5-coordinate geometry to three equivalent Na(1) and two equivalent Mn(1) atoms. In the second O site, O(2) is bonded in a 6-coordinate geometry to three equivalent Na(1) and three equivalent Mn(1) atoms.