RbMgMn4O8 is Orthorhombic Perovskite-derived structured and crystallizes in the monoclinic C2/m space group. Rb(1) is bonded in a 10-coordinate geometry to two equivalent O(1), four equivalent O(2), and four equivalent O(4) atoms. Mg(1) is bonded to two equivalent O(1) and four equivalent O(3) atoms to form MgO6 octahedra that share corners with four equivalent Mn(1)O6 octahedra, edges with two equivalent Mg(1)O6 octahedra, edges with four equivalent Mn(2)O6 octahedra, and faces with two equivalent Mn(1)O6 octahedra. The corner-sharing octahedral tilt angles are 49°. There are two inequivalent Mn sites. In the first Mn site, Mn(1) is bonded to one O(1), two equivalent O(3), and three equivalent O(2) atoms to form distorted MnO6 octahedra that share corners with two equivalent Mg(1)O6 octahedra, corners with four equivalent Mn(2)O6 octahedra, edges with four equivalent Mn(1)O6 octahedra, and  a faceface with one Mg(1)O6 octahedra. The corner-sharing octahedral tilt angles range from 45-49°. In the second Mn site, Mn(2) is bonded to one O(3), two equivalent O(1), and three equivalent O(4) atoms to form MnO6 octahedra that share corners with four equivalent Mn(1)O6 octahedra, edges with two equivalent Mg(1)O6 octahedra, and edges with four equivalent Mn(2)O6 octahedra. The corner-sharing octahedral tilt angles range from 45-49°. There are four inequivalent O sites. In the first O site, O(1) is bonded to one Rb(1), one Mg(1), one Mn(1), and two equivalent Mn(2) atoms to form distorted corner-sharing ORbMgMn3 trigonal pyramids. In the second O site, O(2) is bonded in a 3-coordinate geometry to two equivalent Rb(1) and three equivalent Mn(1) atoms. In the third O site, O(3) is bonded in a 5-coordinate geometry to two equivalent Mg(1), one Mn(2), and two equivalent Mn(1) atoms. In the fourth O site, O(4) is bonded in a 3-coordinate geometry to two equivalent Rb(1) and three equivalent Mn(2) atoms.
RbMgMn4O8 is Orthorhombic Perovskite-derived structured and crystallizes in the monoclinic C2/m space group. Rb(1) is bonded in a 10-coordinate geometry to two equivalent O(1), four equivalent O(2), and four equivalent O(4) atoms. Both Rb(1)-O(1) bond lengths are 3.34 Å. All Rb(1)-O(2) bond lengths are 3.07 Å. All Rb(1)-O(4) bond lengths are 3.20 Å. Mg(1) is bonded to two equivalent O(1) and four equivalent O(3) atoms to form MgO6 octahedra that share corners with four equivalent Mn(1)O6 octahedra, edges with two equivalent Mg(1)O6 octahedra, edges with four equivalent Mn(2)O6 octahedra, and faces with two equivalent Mn(1)O6 octahedra. The corner-sharing octahedral tilt angles are 49°. Both Mg(1)-O(1) bond lengths are 1.97 Å. All Mg(1)-O(3) bond lengths are 2.12 Å. There are two inequivalent Mn sites. In the first Mn site, Mn(1) is bonded to one O(1), two equivalent O(3), and three equivalent O(2) atoms to form distorted MnO6 octahedra that share corners with two equivalent Mg(1)O6 octahedra, corners with four equivalent Mn(2)O6 octahedra, edges with four equivalent Mn(1)O6 octahedra, and  a faceface with one Mg(1)O6 octahedra. The corner-sharing octahedral tilt angles range from 45-49°. The Mn(1)-O(1) bond length is 1.99 Å. Both Mn(1)-O(3) bond lengths are 2.31 Å. There is one shorter (1.93 Å) and two longer (2.01 Å) Mn(1)-O(2) bond lengths. In the second Mn site, Mn(2) is bonded to one O(3), two equivalent O(1), and three equivalent O(4) atoms to form MnO6 octahedra that share corners with four equivalent Mn(1)O6 octahedra, edges with two equivalent Mg(1)O6 octahedra, and edges with four equivalent Mn(2)O6 octahedra. The corner-sharing octahedral tilt angles range from 45-49°. The Mn(2)-O(3) bond length is 2.00 Å. Both Mn(2)-O(1) bond lengths are 2.10 Å. There is one shorter (1.94 Å) and two longer (2.02 Å) Mn(2)-O(4) bond lengths. There are four inequivalent O sites. In the first O site, O(1) is bonded to one Rb(1), one Mg(1), one Mn(1), and two equivalent Mn(2) atoms to form distorted corner-sharing ORbMgMn3 trigonal pyramids. In the second O site, O(2) is bonded in a 3-coordinate geometry to two equivalent Rb(1) and three equivalent Mn(1) atoms. In the third O site, O(3) is bonded in a 5-coordinate geometry to two equivalent Mg(1), one Mn(2), and two equivalent Mn(1) atoms. In the fourth O site, O(4) is bonded in a 3-coordinate geometry to two equivalent Rb(1) and three equivalent Mn(2) atoms.