MgMn4O8 is beta indium sulfide-derived structured and crystallizes in the triclinic P-1 space group. Mg(1) is bonded to two equivalent O(1), two equivalent O(2), and two equivalent O(4) atoms to form MgO6 octahedra that share corners with six equivalent Mn(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 16-22°. There are two inequivalent Mn sites. In the first Mn site, Mn(1) is bonded to one O(3), one O(4), two equivalent O(1), and two equivalent O(2) atoms to form distorted MnO6 octahedra that share corners with three equivalent Mg(1)O6 octahedra,  an edgeedge with one 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 16-22°. In the second Mn site, Mn(2) is bonded to one O(1), one O(2), two equivalent O(3), and two equivalent O(4) atoms to form MnO6 octahedra that share edges with two equivalent Mg(1)O6 octahedra, edges with two equivalent Mn(2)O6 octahedra, and edges with four equivalent Mn(1)O6 octahedra. There are four 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(2), and two equivalent Mn(1) atoms. In the second O site, O(2) is bonded in a distorted rectangular see-saw-like geometry to one Mg(1), one Mn(2), and two equivalent Mn(1) atoms. In the third O site, O(3) is bonded in a distorted trigonal non-coplanar geometry to one Mn(1) and two equivalent Mn(2) atoms. In the fourth O site, O(4) is bonded in a rectangular see-saw-like geometry to one Mg(1), one Mn(1), and two equivalent Mn(2) atoms.
MgMn4O8 is beta indium sulfide-derived structured and crystallizes in the triclinic P-1 space group. Mg(1) is bonded to two equivalent O(1), two equivalent O(2), and two equivalent O(4) atoms to form MgO6 octahedra that share corners with six equivalent Mn(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 16-22°. Both Mg(1)-O(1) bond lengths are 2.10 Å. Both Mg(1)-O(2) bond lengths are 2.12 Å. Both Mg(1)-O(4) bond lengths are 2.17 Å. There are two inequivalent Mn sites. In the first Mn site, Mn(1) is bonded to one O(3), one O(4), two equivalent O(1), and two equivalent O(2) atoms to form distorted MnO6 octahedra that share corners with three equivalent Mg(1)O6 octahedra,  an edgeedge with one 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 16-22°. The Mn(1)-O(3) bond length is 2.03 Å. The Mn(1)-O(4) bond length is 2.04 Å. There is one shorter (1.93 Å) and one longer (2.27 Å) Mn(1)-O(1) bond length. There is one shorter (1.95 Å) and one longer (2.18 Å) Mn(1)-O(2) bond length. In the second Mn site, Mn(2) is bonded to one O(1), one O(2), two equivalent O(3), and two equivalent O(4) atoms to form MnO6 octahedra that share edges with two equivalent Mg(1)O6 octahedra, edges with two equivalent Mn(2)O6 octahedra, and edges with four equivalent Mn(1)O6 octahedra. The Mn(2)-O(1) bond length is 1.92 Å. The Mn(2)-O(2) bond length is 1.93 Å. There is one shorter (1.93 Å) and one longer (1.94 Å) Mn(2)-O(3) bond length. There is one shorter (1.99 Å) and one longer (2.00 Å) Mn(2)-O(4) bond length. There are four 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(2), and two equivalent Mn(1) atoms. In the second O site, O(2) is bonded in a distorted rectangular see-saw-like geometry to one Mg(1), one Mn(2), and two equivalent Mn(1) atoms. In the third O site, O(3) is bonded in a distorted trigonal non-coplanar geometry to one Mn(1) and two equivalent Mn(2) atoms. In the fourth O site, O(4) is bonded in a rectangular see-saw-like geometry to one Mg(1), one Mn(1), and two equivalent Mn(2) atoms.