Li2MgMn3O8 is Spinel-derived structured and crystallizes in the trigonal R-3m space group. Li(1) is bonded to one O(1) and three equivalent O(2) atoms to form LiO4 tetrahedra that share corners with three equivalent Mg(1)O6 octahedra and corners with nine equivalent Mn(1)O6 octahedra. The corner-sharing octahedral tilt angles range from 59-62°. Mg(1) is bonded to six equivalent O(2) atoms to form MgO6 octahedra that share corners with six equivalent Li(1)O4 tetrahedra and edges with six equivalent Mn(1)O6 octahedra. 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 Li(1)O4 tetrahedra, edges with two equivalent Mg(1)O6 octahedra, and edges with four equivalent Mn(1)O6 octahedra. There are two inequivalent O sites. In the first O site, O(1) is bonded to one Li(1) and three equivalent Mn(1) atoms to form distorted OLiMn3 trigonal pyramids that share corners with three equivalent O(1)LiMn3 trigonal pyramids, corners with nine equivalent O(2)LiMgMn2 trigonal pyramids, and edges with three equivalent O(2)LiMgMn2 trigonal pyramids. In the second O site, O(2) is bonded to one Li(1), one Mg(1), and two equivalent Mn(1) atoms to form distorted OLiMgMn2 trigonal pyramids that share corners with three equivalent O(1)LiMn3 trigonal pyramids, corners with nine equivalent O(2)LiMgMn2 trigonal pyramids,  an edgeedge with one O(1)LiMn3 trigonal pyramid, and edges with two equivalent O(2)LiMgMn2 trigonal pyramids.
Li2MgMn3O8 is Spinel-derived structured and crystallizes in the trigonal R-3m space group. Li(1) is bonded to one O(1) and three equivalent O(2) atoms to form LiO4 tetrahedra that share corners with three equivalent Mg(1)O6 octahedra and corners with nine equivalent Mn(1)O6 octahedra. The corner-sharing octahedral tilt angles range from 59-62°. The Li(1)-O(1) bond length is 2.17 Å. All Li(1)-O(2) bond lengths are 1.95 Å. Mg(1) is bonded to six equivalent O(2) atoms to form MgO6 octahedra that share corners with six equivalent Li(1)O4 tetrahedra and edges with six equivalent Mn(1)O6 octahedra. All Mg(1)-O(2) bond lengths are 2.07 Å. 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 Li(1)O4 tetrahedra, edges with two equivalent Mg(1)O6 octahedra, and edges with four equivalent Mn(1)O6 octahedra. Both Mn(1)-O(1) bond lengths are 1.98 Å. All Mn(1)-O(2) bond lengths are 1.93 Å. There are two inequivalent O sites. In the first O site, O(1) is bonded to one Li(1) and three equivalent Mn(1) atoms to form distorted OLiMn3 trigonal pyramids that share corners with three equivalent O(1)LiMn3 trigonal pyramids, corners with nine equivalent O(2)LiMgMn2 trigonal pyramids, and edges with three equivalent O(2)LiMgMn2 trigonal pyramids. In the second O site, O(2) is bonded to one Li(1), one Mg(1), and two equivalent Mn(1) atoms to form distorted OLiMgMn2 trigonal pyramids that share corners with three equivalent O(1)LiMn3 trigonal pyramids, corners with nine equivalent O(2)LiMgMn2 trigonal pyramids,  an edgeedge with one O(1)LiMn3 trigonal pyramid, and edges with two equivalent O(2)LiMgMn2 trigonal pyramids.