NaMgMn4O8 crystallizes in the monoclinic C2/m space group. Na(1) is bonded to two equivalent O(3) and four equivalent O(2) atoms to form NaO6 octahedra that share corners with six equivalent Mn(3)O6 octahedra, edges with two equivalent Mg(1)O6 octahedra, edges with two equivalent Mn(1)O6 octahedra, and edges with four equivalent Mn(2)O6 octahedra. The corner-sharing octahedral tilt angles range from 13-15°. Mg(1) is bonded to two equivalent O(1) and four equivalent O(2) atoms to form distorted MgO6 octahedra that share corners with six equivalent Mn(1)O6 octahedra, edges with two equivalent Na(1)O6 octahedra, edges with two equivalent Mn(3)O6 octahedra, and edges with four equivalent Mn(2)O6 octahedra. The corner-sharing octahedral tilt angles range from 14-16°. There are three inequivalent Mn sites. In the first Mn site, Mn(1) is bonded to two equivalent O(1) and four equivalent O(2) atoms to form MnO6 octahedra that share corners with six equivalent Mg(1)O6 octahedra, edges with two equivalent Na(1)O6 octahedra, edges with two equivalent Mn(3)O6 octahedra, and edges with four equivalent Mn(2)O6 octahedra. The corner-sharing octahedral tilt angles range from 14-16°. In the second Mn site, Mn(2) is bonded to two equivalent O(1), two equivalent O(2), and two equivalent O(3) atoms to form MnO6 octahedra that share edges with two equivalent Na(1)O6 octahedra, edges with two equivalent Mg(1)O6 octahedra, edges with two equivalent Mn(1)O6 octahedra, edges with two equivalent Mn(2)O6 octahedra, and edges with two equivalent Mn(3)O6 octahedra. In the third Mn site, Mn(3) is bonded to two equivalent O(3) and four equivalent O(2) atoms to form MnO6 octahedra that share corners with six equivalent Na(1)O6 octahedra, edges with two equivalent Mg(1)O6 octahedra, edges with two equivalent Mn(1)O6 octahedra, and edges with four equivalent Mn(2)O6 octahedra. The corner-sharing octahedral tilt angles range from 13-15°. There are three inequivalent O sites. In the first O site, O(1) is bonded in a rectangular see-saw-like geometry to one Mg(1), one Mn(1), and two equivalent Mn(2) atoms. In the second O site, O(2) is bonded to one Na(1), one Mg(1), one Mn(1), one Mn(2), and one Mn(3) atom to form a mixture of corner and edge-sharing ONaMgMn3 square pyramids. In the third O site, O(3) is bonded in a see-saw-like geometry to one Na(1), one Mn(3), and two equivalent Mn(2) atoms.
NaMgMn4O8 crystallizes in the monoclinic C2/m space group. Na(1) is bonded to two equivalent O(3) and four equivalent O(2) atoms to form NaO6 octahedra that share corners with six equivalent Mn(3)O6 octahedra, edges with two equivalent Mg(1)O6 octahedra, edges with two equivalent Mn(1)O6 octahedra, and edges with four equivalent Mn(2)O6 octahedra. The corner-sharing octahedral tilt angles range from 13-15°. Both Na(1)-O(3) bond lengths are 2.23 Å. All Na(1)-O(2) bond lengths are 2.34 Å. Mg(1) is bonded to two equivalent O(1) and four equivalent O(2) atoms to form distorted MgO6 octahedra that share corners with six equivalent Mn(1)O6 octahedra, edges with two equivalent Na(1)O6 octahedra, edges with two equivalent Mn(3)O6 octahedra, and edges with four equivalent Mn(2)O6 octahedra. The corner-sharing octahedral tilt angles range from 14-16°. Both Mg(1)-O(1) bond lengths are 2.19 Å. All Mg(1)-O(2) bond lengths are 2.15 Å. There are three inequivalent Mn sites. In the first Mn site, Mn(1) is bonded to two equivalent O(1) and four equivalent O(2) atoms to form MnO6 octahedra that share corners with six equivalent Mg(1)O6 octahedra, edges with two equivalent Na(1)O6 octahedra, edges with two equivalent Mn(3)O6 octahedra, and edges with four equivalent Mn(2)O6 octahedra. The corner-sharing octahedral tilt angles range from 14-16°. Both Mn(1)-O(1) bond lengths are 2.25 Å. All Mn(1)-O(2) bond lengths are 2.19 Å. In the second Mn site, Mn(2) is bonded to two equivalent O(1), two equivalent O(2), and two equivalent O(3) atoms to form MnO6 octahedra that share edges with two equivalent Na(1)O6 octahedra, edges with two equivalent Mg(1)O6 octahedra, edges with two equivalent Mn(1)O6 octahedra, edges with two equivalent Mn(2)O6 octahedra, and edges with two equivalent Mn(3)O6 octahedra. Both Mn(2)-O(1) bond lengths are 1.97 Å. Both Mn(2)-O(2) bond lengths are 1.96 Å. Both Mn(2)-O(3) bond lengths are 1.95 Å. In the third Mn site, Mn(3) is bonded to two equivalent O(3) and four equivalent O(2) atoms to form MnO6 octahedra that share corners with six equivalent Na(1)O6 octahedra, edges with two equivalent Mg(1)O6 octahedra, edges with two equivalent Mn(1)O6 octahedra, and edges with four equivalent Mn(2)O6 octahedra. The corner-sharing octahedral tilt angles range from 13-15°. Both Mn(3)-O(3) bond lengths are 2.23 Å. All Mn(3)-O(2) bond lengths are 1.99 Å. There are three inequivalent O sites. In the first O site, O(1) is bonded in a rectangular see-saw-like geometry to one Mg(1), one Mn(1), and two equivalent Mn(2) atoms. In the second O site, O(2) is bonded to one Na(1), one Mg(1), one Mn(1), one Mn(2), and one Mn(3) atom to form a mixture of corner and edge-sharing ONaMgMn3 square pyramids. In the third O site, O(3) is bonded in a see-saw-like geometry to one Na(1), one Mn(3), and two equivalent Mn(2) atoms.