Mg2Mn3O8 is beta indium sulfide-derived structured and crystallizes in the trigonal R3m space group. There are two inequivalent Mg sites. In the first Mg site, Mg(1) is bonded to one O(1) and three equivalent O(2) atoms to form MgO4 tetrahedra that share corners with three equivalent Mg(2)O6 octahedra and corners with nine equivalent Mn(1)O6 octahedra. The corner-sharing octahedral tilt angles range from 59-62°. In the second Mg site, Mg(2) is bonded to three equivalent O(2) and three equivalent O(3) atoms to form MgO6 octahedra that share corners with three equivalent Mg(1)O4 tetrahedra and edges with six equivalent Mn(1)O6 octahedra. Mn(1) is bonded to one O(1), one O(4), two equivalent O(2), and two equivalent O(3) atoms to form MnO6 octahedra that share corners with three equivalent Mg(1)O4 tetrahedra, edges with two equivalent Mg(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 to one Mg(1) and three equivalent Mn(1) atoms to form a mixture of distorted corner and edge-sharing OMgMn3 trigonal pyramids. In the second O site, O(2) is bonded to one Mg(1), one Mg(2), and two equivalent Mn(1) atoms to form distorted OMg2Mn2 tetrahedra that share corners with two equivalent O(2)Mg2Mn2 tetrahedra,  a cornercorner with one O(1)MgMn3 trigonal pyramid, edges with two equivalent O(2)Mg2Mn2 tetrahedra, and  an edgeedge with one O(1)MgMn3 trigonal pyramid. In the third O site, O(3) is bonded in a distorted T-shaped geometry to one Mg(2) and two equivalent Mn(1) atoms. In the fourth O site, O(4) is bonded in a distorted T-shaped geometry to three equivalent Mn(1) atoms.
Mg2Mn3O8 is beta indium sulfide-derived structured and crystallizes in the trigonal R3m space group. There are two inequivalent Mg sites. In the first Mg site, Mg(1) is bonded to one O(1) and three equivalent O(2) atoms to form MgO4 tetrahedra that share corners with three equivalent Mg(2)O6 octahedra and corners with nine equivalent Mn(1)O6 octahedra. The corner-sharing octahedral tilt angles range from 59-62°. The Mg(1)-O(1) bond length is 2.09 Å. All Mg(1)-O(2) bond lengths are 1.96 Å. In the second Mg site, Mg(2) is bonded to three equivalent O(2) and three equivalent O(3) atoms to form MgO6 octahedra that share corners with three equivalent Mg(1)O4 tetrahedra and edges with six equivalent Mn(1)O6 octahedra. All Mg(2)-O(2) bond lengths are 2.06 Å. All Mg(2)-O(3) bond lengths are 2.09 Å. Mn(1) is bonded to one O(1), one O(4), two equivalent O(2), and two equivalent O(3) atoms to form MnO6 octahedra that share corners with three equivalent Mg(1)O4 tetrahedra, edges with two equivalent Mg(2)O6 octahedra, and edges with four equivalent Mn(1)O6 octahedra. The Mn(1)-O(1) bond length is 2.02 Å. The Mn(1)-O(4) bond length is 1.95 Å. Both Mn(1)-O(2) bond lengths are 1.97 Å. Both Mn(1)-O(3) bond lengths are 1.89 Å. There are four inequivalent O sites. In the first O site, O(1) is bonded to one Mg(1) and three equivalent Mn(1) atoms to form a mixture of distorted corner and edge-sharing OMgMn3 trigonal pyramids. In the second O site, O(2) is bonded to one Mg(1), one Mg(2), and two equivalent Mn(1) atoms to form distorted OMg2Mn2 tetrahedra that share corners with two equivalent O(2)Mg2Mn2 tetrahedra,  a cornercorner with one O(1)MgMn3 trigonal pyramid, edges with two equivalent O(2)Mg2Mn2 tetrahedra, and  an edgeedge with one O(1)MgMn3 trigonal pyramid. In the third O site, O(3) is bonded in a distorted T-shaped geometry to one Mg(2) and two equivalent Mn(1) atoms. In the fourth O site, O(4) is bonded in a distorted T-shaped geometry to three equivalent Mn(1) atoms.