Li3Mn4O8 crystallizes in the monoclinic C2/m space group. There are two inequivalent Li sites. In the first Li site, Li(1) is bonded to two equivalent O(1), two equivalent O(2), and two equivalent O(3) atoms to form LiO6 octahedra that share corners with four equivalent Li(2)O6 octahedra, corners with four equivalent Mn(1)O6 octahedra, corners with two equivalent Mn(2)O5 square pyramids, edges with two equivalent Li(1)O6 octahedra, edges with two equivalent Mn(2)O5 square pyramids, and faces with two equivalent Mn(1)O6 octahedra. The corner-sharing octahedral tilt angles range from 39-53°. In the second Li site, Li(2) is bonded to two equivalent O(2) and four equivalent O(3) atoms to form distorted LiO6 octahedra that share corners with eight equivalent Li(1)O6 octahedra, corners with four equivalent Mn(2)O5 square pyramids, edges with four equivalent Mn(1)O6 octahedra, and edges with two equivalent Mn(2)O5 square pyramids. The corner-sharing octahedral tilt angles range from 39-53°. There are two inequivalent Mn sites. In the first Mn site, Mn(1) is bonded to two equivalent O(1), two equivalent O(2), and two equivalent O(3) atoms to form MnO6 octahedra that share corners with four equivalent Li(1)O6 octahedra, corners with six equivalent Mn(2)O5 square pyramids, edges with two equivalent Li(2)O6 octahedra, edges with two equivalent Mn(1)O6 octahedra, and faces with two equivalent Li(1)O6 octahedra. The corner-sharing octahedral tilt angles range from 43-44°. In the second Mn site, Mn(2) is bonded to one O(1) and four equivalent O(3) atoms to form distorted MnO5 square pyramids that share corners with two equivalent Li(1)O6 octahedra, corners with two equivalent Li(2)O6 octahedra, corners with six equivalent Mn(1)O6 octahedra,  an edgeedge with one Li(2)O6 octahedra, edges with two equivalent Li(1)O6 octahedra, and edges with two equivalent Mn(2)O5 square pyramids. The corner-sharing octahedral tilt angles range from 46-79°. There are three inequivalent O sites. In the first O site, O(1) is bonded in a 5-coordinate geometry to two equivalent Li(1), one Mn(2), and two equivalent Mn(1) atoms. In the second O site, O(2) is bonded in a 5-coordinate geometry to one Li(2), two equivalent Li(1), and two equivalent Mn(1) atoms. In the third O site, O(3) is bonded to one Li(1), one Li(2), one Mn(1), and two equivalent Mn(2) atoms to form a mixture of distorted corner and edge-sharing OLi2Mn3 trigonal bipyramids.
Li3Mn4O8 crystallizes in the monoclinic C2/m space group. There are two inequivalent Li sites. In the first Li site, Li(1) is bonded to two equivalent O(1), two equivalent O(2), and two equivalent O(3) atoms to form LiO6 octahedra that share corners with four equivalent Li(2)O6 octahedra, corners with four equivalent Mn(1)O6 octahedra, corners with two equivalent Mn(2)O5 square pyramids, edges with two equivalent Li(1)O6 octahedra, edges with two equivalent Mn(2)O5 square pyramids, and faces with two equivalent Mn(1)O6 octahedra. The corner-sharing octahedral tilt angles range from 39-53°. Both Li(1)-O(1) bond lengths are 2.21 Å. Both Li(1)-O(2) bond lengths are 2.09 Å. Both Li(1)-O(3) bond lengths are 2.05 Å. In the second Li site, Li(2) is bonded to two equivalent O(2) and four equivalent O(3) atoms to form distorted LiO6 octahedra that share corners with eight equivalent Li(1)O6 octahedra, corners with four equivalent Mn(2)O5 square pyramids, edges with four equivalent Mn(1)O6 octahedra, and edges with two equivalent Mn(2)O5 square pyramids. The corner-sharing octahedral tilt angles range from 39-53°. Both Li(2)-O(2) bond lengths are 2.00 Å. All Li(2)-O(3) bond lengths are 2.29 Å. There are two inequivalent Mn sites. In the first Mn site, Mn(1) is bonded to two equivalent O(1), two equivalent O(2), and two equivalent O(3) atoms to form MnO6 octahedra that share corners with four equivalent Li(1)O6 octahedra, corners with six equivalent Mn(2)O5 square pyramids, edges with two equivalent Li(2)O6 octahedra, edges with two equivalent Mn(1)O6 octahedra, and faces with two equivalent Li(1)O6 octahedra. The corner-sharing octahedral tilt angles range from 43-44°. Both Mn(1)-O(1) bond lengths are 1.98 Å. Both Mn(1)-O(2) bond lengths are 1.94 Å. Both Mn(1)-O(3) bond lengths are 2.11 Å. In the second Mn site, Mn(2) is bonded to one O(1) and four equivalent O(3) atoms to form distorted MnO5 square pyramids that share corners with two equivalent Li(1)O6 octahedra, corners with two equivalent Li(2)O6 octahedra, corners with six equivalent Mn(1)O6 octahedra,  an edgeedge with one Li(2)O6 octahedra, edges with two equivalent Li(1)O6 octahedra, and edges with two equivalent Mn(2)O5 square pyramids. The corner-sharing octahedral tilt angles range from 46-79°. The Mn(2)-O(1) bond length is 2.14 Å. There are two shorter (1.95 Å) and two longer (1.98 Å) Mn(2)-O(3) bond lengths. There are three inequivalent O sites. In the first O site, O(1) is bonded in a 5-coordinate geometry to two equivalent Li(1), one Mn(2), and two equivalent Mn(1) atoms. In the second O site, O(2) is bonded in a 5-coordinate geometry to one Li(2), two equivalent Li(1), and two equivalent Mn(1) atoms. In the third O site, O(3) is bonded to one Li(1), one Li(2), one Mn(1), and two equivalent Mn(2) atoms to form a mixture of distorted corner and edge-sharing OLi2Mn3 trigonal bipyramids.