Na4MgMn4O8 crystallizes in the tetragonal I-4m2 space group. Na(1) is bonded in a 5-coordinate geometry to two equivalent O(1) and three equivalent O(2) atoms. Mg(1) is bonded to four equivalent O(1) atoms to form MgO4 tetrahedra that share corners with eight equivalent Mn(1)O5 square pyramids. Mn(1) is bonded to two equivalent O(1) and three equivalent O(2) atoms to form MnO5 square pyramids that share corners with two equivalent Mg(1)O4 tetrahedra and edges with four equivalent Mn(1)O5 square pyramids. There are two inequivalent O sites. In the first O site, O(1) is bonded in a 5-coordinate geometry to two equivalent Na(1), one Mg(1), and two equivalent Mn(1) atoms. In the second O site, O(2) is bonded to three equivalent Na(1) and three equivalent Mn(1) atoms to form distorted edge-sharing ONa3Mn3 octahedra.
Na4MgMn4O8 crystallizes in the tetragonal I-4m2 space group. Na(1) is bonded in a 5-coordinate geometry to two equivalent O(1) and three equivalent O(2) atoms. Both Na(1)-O(1) bond lengths are 2.37 Å. There are two shorter (2.38 Å) and one longer (2.48 Å) Na(1)-O(2) bond length. Mg(1) is bonded to four equivalent O(1) atoms to form MgO4 tetrahedra that share corners with eight equivalent Mn(1)O5 square pyramids. All Mg(1)-O(1) bond lengths are 1.99 Å. Mn(1) is bonded to two equivalent O(1) and three equivalent O(2) atoms to form MnO5 square pyramids that share corners with two equivalent Mg(1)O4 tetrahedra and edges with four equivalent Mn(1)O5 square pyramids. Both Mn(1)-O(1) bond lengths are 2.06 Å. There are two shorter (2.07 Å) and one longer (2.38 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 two equivalent Na(1), one Mg(1), and two equivalent Mn(1) atoms. In the second O site, O(2) is bonded to three equivalent Na(1) and three equivalent Mn(1) atoms to form distorted edge-sharing ONa3Mn3 octahedra.