Mg3Mn4O7 is Caswellsilverite-like structured and crystallizes in the orthorhombic Immm space group. There are two inequivalent Mg sites. In the first Mg site, Mg(1) is bonded to two equivalent O(3) and four equivalent O(1) atoms to form MgO6 octahedra that share corners with two equivalent Mg(1)O6 octahedra, corners with four equivalent Mg(2)O6 octahedra, edges with two equivalent Mg(1)O6 octahedra, edges with two equivalent Mg(2)O6 octahedra, and edges with eight equivalent Mn(2)O6 octahedra. The corner-sharing octahedra are not tilted. In the second Mg site, Mg(2) 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 two equivalent Mg(1)O6 octahedra, corners with two equivalent Mg(2)O6 octahedra, corners with two equivalent Mn(1)O6 octahedra,  an edgeedge with one Mg(1)O6 octahedra, edges with two equivalent Mg(2)O6 octahedra, edges with four equivalent Mn(2)O6 octahedra, and edges with five equivalent Mn(1)O6 octahedra. The corner-sharing octahedral tilt angles range from 0-4°. There are two inequivalent Mn sites. In the first Mn site, Mn(1) is bonded to two equivalent O(4) and four equivalent O(2) atoms to form MnO6 octahedra that share corners with two equivalent Mg(2)O6 octahedra, corners with two equivalent Mn(1)O6 octahedra, corners with two equivalent Mn(2)O6 octahedra,  an edgeedge with one Mn(2)O6 octahedra, edges with five equivalent Mg(2)O6 octahedra, and edges with six equivalent Mn(1)O6 octahedra. The corner-sharing octahedral tilt angles range from 0-6°. In the second Mn site, Mn(2) is bonded to two equivalent O(1), two equivalent O(3), and two equivalent O(4) atoms to form MnO6 octahedra that share corners with two equivalent Mn(1)O6 octahedra, corners with four equivalent Mn(2)O6 octahedra,  an edgeedge with one Mn(1)O6 octahedra, edges with three equivalent Mn(2)O6 octahedra, edges with four equivalent Mg(1)O6 octahedra, and edges with four equivalent Mg(2)O6 octahedra. The corner-sharing octahedral tilt angles range from 0-1°. There are four inequivalent O sites. In the first O site, O(1) is bonded to two equivalent Mg(1), two equivalent Mg(2), and two equivalent Mn(2) atoms to form OMg4Mn2 octahedra that share corners with two equivalent O(2)Mg2Mn4 octahedra, corners with four equivalent O(1)Mg4Mn2 octahedra,  an edgeedge with one O(2)Mg2Mn4 octahedra, edges with three equivalent O(1)Mg4Mn2 octahedra, edges with four equivalent O(3)Mg2Mn4 octahedra, and edges with four equivalent O(4)Mg2Mn4 octahedra. The corner-sharing octahedral tilt angles range from 0-1°. In the second O site, O(2) is bonded to two equivalent Mg(2) and four equivalent Mn(1) atoms to form OMg2Mn4 octahedra that share corners with two equivalent O(2)Mg2Mn4 octahedra, corners with two equivalent O(4)Mg2Mn4 octahedra, corners with two equivalent O(1)Mg4Mn2 octahedra,  an edgeedge with one O(1)Mg4Mn2 octahedra, edges with five equivalent O(4)Mg2Mn4 octahedra, and edges with six equivalent O(2)Mg2Mn4 octahedra. The corner-sharing octahedral tilt angles range from 1-6°. In the third O site, O(3) is bonded to two equivalent Mg(1) and four equivalent Mn(2) atoms to form OMg2Mn4 octahedra that share corners with two equivalent O(3)Mg2Mn4 octahedra, corners with four equivalent O(4)Mg2Mn4 octahedra, edges with two equivalent O(3)Mg2Mn4 octahedra, edges with two equivalent O(4)Mg2Mn4 octahedra, and edges with eight equivalent O(1)Mg4Mn2 octahedra. The corner-sharing octahedra are not tilted. In the fourth O site, O(4) is bonded to two equivalent Mg(2), two equivalent Mn(1), and two equivalent Mn(2) atoms to form OMg2Mn4 octahedra that share corners with two equivalent O(2)Mg2Mn4 octahedra, corners with two equivalent O(3)Mg2Mn4 octahedra, corners with two equivalent O(4)Mg2Mn4 octahedra,  an edgeedge with one O(3)Mg2Mn4 octahedra, edges with two equivalent O(4)Mg2Mn4 octahedra, edges with four equivalent O(1)Mg4Mn2 octahedra, and edges with five equivalent O(2)Mg2Mn4 octahedra. The corner-sharing octahedral tilt angles range from 0-2°.
Mg3Mn4O7 is Caswellsilverite-like structured and crystallizes in the orthorhombic Immm space group. There are two inequivalent Mg sites. In the first Mg site, Mg(1) is bonded to two equivalent O(3) and four equivalent O(1) atoms to form MgO6 octahedra that share corners with two equivalent Mg(1)O6 octahedra, corners with four equivalent Mg(2)O6 octahedra, edges with two equivalent Mg(1)O6 octahedra, edges with two equivalent Mg(2)O6 octahedra, and edges with eight equivalent Mn(2)O6 octahedra. The corner-sharing octahedra are not tilted. Both Mg(1)-O(3) bond lengths are 2.21 Å. All Mg(1)-O(1) bond lengths are 2.19 Å. In the second Mg site, Mg(2) 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 two equivalent Mg(1)O6 octahedra, corners with two equivalent Mg(2)O6 octahedra, corners with two equivalent Mn(1)O6 octahedra,  an edgeedge with one Mg(1)O6 octahedra, edges with two equivalent Mg(2)O6 octahedra, edges with four equivalent Mn(2)O6 octahedra, and edges with five equivalent Mn(1)O6 octahedra. The corner-sharing octahedral tilt angles range from 0-4°. Both Mg(2)-O(1) bond lengths are 2.20 Å. Both Mg(2)-O(2) bond lengths are 2.16 Å. Both Mg(2)-O(4) bond lengths are 2.21 Å. There are two inequivalent Mn sites. In the first Mn site, Mn(1) is bonded to two equivalent O(4) and four equivalent O(2) atoms to form MnO6 octahedra that share corners with two equivalent Mg(2)O6 octahedra, corners with two equivalent Mn(1)O6 octahedra, corners with two equivalent Mn(2)O6 octahedra,  an edgeedge with one Mn(2)O6 octahedra, edges with five equivalent Mg(2)O6 octahedra, and edges with six equivalent Mn(1)O6 octahedra. The corner-sharing octahedral tilt angles range from 0-6°. Both Mn(1)-O(4) bond lengths are 2.21 Å. There are two shorter (2.21 Å) and two longer (2.29 Å) Mn(1)-O(2) bond lengths. In the second Mn site, Mn(2) is bonded to two equivalent O(1), two equivalent O(3), and two equivalent O(4) atoms to form MnO6 octahedra that share corners with two equivalent Mn(1)O6 octahedra, corners with four equivalent Mn(2)O6 octahedra,  an edgeedge with one Mn(1)O6 octahedra, edges with three equivalent Mn(2)O6 octahedra, edges with four equivalent Mg(1)O6 octahedra, and edges with four equivalent Mg(2)O6 octahedra. The corner-sharing octahedral tilt angles range from 0-1°. Both Mn(2)-O(1) bond lengths are 2.21 Å. Both Mn(2)-O(3) bond lengths are 2.20 Å. Both Mn(2)-O(4) bond lengths are 2.21 Å. There are four inequivalent O sites. In the first O site, O(1) is bonded to two equivalent Mg(1), two equivalent Mg(2), and two equivalent Mn(2) atoms to form OMg4Mn2 octahedra that share corners with two equivalent O(2)Mg2Mn4 octahedra, corners with four equivalent O(1)Mg4Mn2 octahedra,  an edgeedge with one O(2)Mg2Mn4 octahedra, edges with three equivalent O(1)Mg4Mn2 octahedra, edges with four equivalent O(3)Mg2Mn4 octahedra, and edges with four equivalent O(4)Mg2Mn4 octahedra. The corner-sharing octahedral tilt angles range from 0-1°. In the second O site, O(2) is bonded to two equivalent Mg(2) and four equivalent Mn(1) atoms to form OMg2Mn4 octahedra that share corners with two equivalent O(2)Mg2Mn4 octahedra, corners with two equivalent O(4)Mg2Mn4 octahedra, corners with two equivalent O(1)Mg4Mn2 octahedra,  an edgeedge with one O(1)Mg4Mn2 octahedra, edges with five equivalent O(4)Mg2Mn4 octahedra, and edges with six equivalent O(2)Mg2Mn4 octahedra. The corner-sharing octahedral tilt angles range from 1-6°. In the third O site, O(3) is bonded to two equivalent Mg(1) and four equivalent Mn(2) atoms to form OMg2Mn4 octahedra that share corners with two equivalent O(3)Mg2Mn4 octahedra, corners with four equivalent O(4)Mg2Mn4 octahedra, edges with two equivalent O(3)Mg2Mn4 octahedra, edges with two equivalent O(4)Mg2Mn4 octahedra, and edges with eight equivalent O(1)Mg4Mn2 octahedra. The corner-sharing octahedra are not tilted. In the fourth O site, O(4) is bonded to two equivalent Mg(2), two equivalent Mn(1), and two equivalent Mn(2) atoms to form OMg2Mn4 octahedra that share corners with two equivalent O(2)Mg2Mn4 octahedra, corners with two equivalent O(3)Mg2Mn4 octahedra, corners with two equivalent O(4)Mg2Mn4 octahedra,  an edgeedge with one O(3)Mg2Mn4 octahedra, edges with two equivalent O(4)Mg2Mn4 octahedra, edges with four equivalent O(1)Mg4Mn2 octahedra, and edges with five equivalent O(2)Mg2Mn4 octahedra. The corner-sharing octahedral tilt angles range from 0-2°.