MgMn2O4 crystallizes in the monoclinic P2_1/c space group. Mg(1) is bonded to one O(2), one O(4), two equivalent O(1), and two equivalent O(3) atoms to form MgO6 octahedra that share corners with two equivalent Mg(1)O6 octahedra, corners with three equivalent Mn(1)O5 trigonal bipyramids,  an edgeedge with one Mg(1)O6 octahedra, and edges with two equivalent Mn(1)O5 trigonal bipyramids. The corner-sharing octahedral tilt angles are 43°. There are two inequivalent Mn sites. In the first Mn site, Mn(1) is bonded to one O(1), one O(3), one O(4), and two equivalent O(2) atoms to form distorted MnO5 trigonal bipyramids that share corners with three equivalent Mg(1)O6 octahedra, corners with two equivalent Mn(1)O5 trigonal bipyramids, and edges with two equivalent Mg(1)O6 octahedra. The corner-sharing octahedral tilt angles range from 49-56°. In the second Mn site, Mn(2) is bonded in a 6-coordinate geometry to one O(2), one O(3), two equivalent O(1), and two equivalent O(4) atoms. There are four inequivalent O sites. In the first O site, O(1) is bonded in a 5-coordinate geometry to two equivalent Mg(1), one Mn(1), and two equivalent Mn(2) atoms. In the second O site, O(2) is bonded to one Mg(1), one Mn(2), and two equivalent Mn(1) atoms to form distorted corner-sharing OMgMn3 trigonal pyramids. In the third O site, O(3) is bonded in a 4-coordinate geometry to two equivalent Mg(1), one Mn(1), and one Mn(2) atom. In the fourth O site, O(4) is bonded to one Mg(1), one Mn(1), and two equivalent Mn(2) atoms to form a mixture of edge and corner-sharing OMgMn3 trigonal pyramids.
MgMn2O4 crystallizes in the monoclinic P2_1/c space group. Mg(1) is bonded to one O(2), one O(4), two equivalent O(1), and two equivalent O(3) atoms to form MgO6 octahedra that share corners with two equivalent Mg(1)O6 octahedra, corners with three equivalent Mn(1)O5 trigonal bipyramids,  an edgeedge with one Mg(1)O6 octahedra, and edges with two equivalent Mn(1)O5 trigonal bipyramids. The corner-sharing octahedral tilt angles are 43°. The Mg(1)-O(2) bond length is 2.09 Å. The Mg(1)-O(4) bond length is 2.10 Å. There is one shorter (2.19 Å) and one longer (2.26 Å) Mg(1)-O(1) bond length. There is one shorter (2.10 Å) and one longer (2.13 Å) Mg(1)-O(3) bond length. There are two inequivalent Mn sites. In the first Mn site, Mn(1) is bonded to one O(1), one O(3), one O(4), and two equivalent O(2) atoms to form distorted MnO5 trigonal bipyramids that share corners with three equivalent Mg(1)O6 octahedra, corners with two equivalent Mn(1)O5 trigonal bipyramids, and edges with two equivalent Mg(1)O6 octahedra. The corner-sharing octahedral tilt angles range from 49-56°. The Mn(1)-O(1) bond length is 1.99 Å. The Mn(1)-O(3) bond length is 1.96 Å. The Mn(1)-O(4) bond length is 1.95 Å. There is one shorter (1.99 Å) and one longer (2.13 Å) Mn(1)-O(2) bond length. In the second Mn site, Mn(2) is bonded in a 6-coordinate geometry to one O(2), one O(3), two equivalent O(1), and two equivalent O(4) atoms. The Mn(2)-O(2) bond length is 1.93 Å. The Mn(2)-O(3) bond length is 2.01 Å. There is one shorter (1.97 Å) and one longer (2.54 Å) Mn(2)-O(1) bond length. There is one shorter (1.95 Å) and one longer (2.21 Å) Mn(2)-O(4) bond length. There are four inequivalent O sites. In the first O site, O(1) is bonded in a 5-coordinate geometry to two equivalent Mg(1), one Mn(1), and two equivalent Mn(2) atoms. In the second O site, O(2) is bonded to one Mg(1), one Mn(2), and two equivalent Mn(1) atoms to form distorted corner-sharing OMgMn3 trigonal pyramids. In the third O site, O(3) is bonded in a 4-coordinate geometry to two equivalent Mg(1), one Mn(1), and one Mn(2) atom. In the fourth O site, O(4) is bonded to one Mg(1), one Mn(1), and two equivalent Mn(2) atoms to form a mixture of edge and corner-sharing OMgMn3 trigonal pyramids.