Ba5Sm8Mn4O21 crystallizes in the tetragonal I4/m space group. There are two inequivalent Ba sites. In the first Ba site, Ba(1) is bonded in a 10-coordinate geometry to two equivalent O(2), four equivalent O(1), and four equivalent O(3) atoms. In the second Ba site, Ba(2) is bonded in a distorted q6 geometry to two equivalent O(4) and eight equivalent O(2) atoms. There are two inequivalent Sm sites. In the first Sm site, Sm(1) is bonded to one O(4), two equivalent O(1), and four equivalent O(2) atoms to form distorted SmO7 pentagonal bipyramids that share  a cornercorner with one Sm(1)O7 pentagonal bipyramid, corners with two equivalent Mn(1)O5 trigonal bipyramids, edges with two equivalent Mn(1)O5 trigonal bipyramids, and faces with two equivalent Sm(1)O7 pentagonal bipyramids. In the second Sm site, Sm(2) is bonded in a 7-coordinate geometry to one O(3), two equivalent O(2), and four equivalent O(1) atoms. Mn(1) is bonded to one O(3), two equivalent O(1), and two equivalent O(2) atoms to form distorted MnO5 trigonal bipyramids that share corners with two equivalent Sm(1)O7 pentagonal bipyramids and edges with two equivalent Sm(1)O7 pentagonal bipyramids. There are four inequivalent O sites. In the first O site, O(1) is bonded in a 4-coordinate geometry to two equivalent Ba(1), one Sm(1), two equivalent Sm(2), and one Mn(1) atom. In the second O site, O(2) is bonded to one Ba(1), one Ba(2), one Sm(2), two equivalent Sm(1), and one Mn(1) atom to form distorted OBa2Sm3Mn octahedra that share  a cornercorner with one O(4)Ba2Sm4 octahedra, corners with three equivalent O(3)Ba4SmMn octahedra, corners with six equivalent O(2)Ba2Sm3Mn octahedra, edges with two equivalent O(2)Ba2Sm3Mn octahedra,  a faceface with one O(4)Ba2Sm4 octahedra,  a faceface with one O(3)Ba4SmMn octahedra, and faces with two equivalent O(2)Ba2Sm3Mn octahedra. The corner-sharing octahedral tilt angles range from 0-76°. In the third O site, O(3) is bonded to four equivalent Ba(1), one Sm(2), and one Mn(1) atom to form distorted OBa4SmMn octahedra that share corners with two equivalent O(3)Ba4SmMn octahedra, corners with six equivalent O(2)Ba2Sm3Mn octahedra, edges with five equivalent O(3)Ba4SmMn octahedra, and faces with two equivalent O(2)Ba2Sm3Mn octahedra. The corner-sharing octahedral tilt angles range from 7-58°. In the fourth O site, O(4) is bonded to two equivalent Ba(2) and four equivalent Sm(1) atoms to form OBa2Sm4 octahedra that share corners with two equivalent O(4)Ba2Sm4 octahedra, corners with eight equivalent O(2)Ba2Sm3Mn octahedra, and faces with eight equivalent O(2)Ba2Sm3Mn octahedra. The corner-sharing octahedral tilt angles range from 0-61°.
Ba5Sm8Mn4O21 crystallizes in the tetragonal I4/m space group. There are two inequivalent Ba sites. In the first Ba site, Ba(1) is bonded in a 10-coordinate geometry to two equivalent O(2), four equivalent O(1), and four equivalent O(3) atoms. Both Ba(1)-O(2) bond lengths are 3.03 Å. All Ba(1)-O(1) bond lengths are 3.33 Å. There are a spread of Ba(1)-O(3) bond distances ranging from 2.66-2.95 Å. In the second Ba site, Ba(2) is bonded in a distorted q6 geometry to two equivalent O(4) and eight equivalent O(2) atoms. Both Ba(2)-O(4) bond lengths are 2.95 Å. All Ba(2)-O(2) bond lengths are 3.01 Å. There are two inequivalent Sm sites. In the first Sm site, Sm(1) is bonded to one O(4), two equivalent O(1), and four equivalent O(2) atoms to form distorted SmO7 pentagonal bipyramids that share  a cornercorner with one Sm(1)O7 pentagonal bipyramid, corners with two equivalent Mn(1)O5 trigonal bipyramids, edges with two equivalent Mn(1)O5 trigonal bipyramids, and faces with two equivalent Sm(1)O7 pentagonal bipyramids. The Sm(1)-O(4) bond length is 2.39 Å. Both Sm(1)-O(1) bond lengths are 2.38 Å. There are two shorter (2.38 Å) and two longer (2.49 Å) Sm(1)-O(2) bond lengths. In the second Sm site, Sm(2) is bonded in a 7-coordinate geometry to one O(3), two equivalent O(2), and four equivalent O(1) atoms. The Sm(2)-O(3) bond length is 2.66 Å. Both Sm(2)-O(2) bond lengths are 2.48 Å. There are two shorter (2.34 Å) and two longer (2.40 Å) Sm(2)-O(1) bond lengths. Mn(1) is bonded to one O(3), two equivalent O(1), and two equivalent O(2) atoms to form distorted MnO5 trigonal bipyramids that share corners with two equivalent Sm(1)O7 pentagonal bipyramids and edges with two equivalent Sm(1)O7 pentagonal bipyramids. The Mn(1)-O(3) bond length is 2.08 Å. Both Mn(1)-O(1) bond lengths are 2.13 Å. Both Mn(1)-O(2) bond lengths are 2.18 Å. There are four inequivalent O sites. In the first O site, O(1) is bonded in a 4-coordinate geometry to two equivalent Ba(1), one Sm(1), two equivalent Sm(2), and one Mn(1) atom. In the second O site, O(2) is bonded to one Ba(1), one Ba(2), one Sm(2), two equivalent Sm(1), and one Mn(1) atom to form distorted OBa2Sm3Mn octahedra that share  a cornercorner with one O(4)Ba2Sm4 octahedra, corners with three equivalent O(3)Ba4SmMn octahedra, corners with six equivalent O(2)Ba2Sm3Mn octahedra, edges with two equivalent O(2)Ba2Sm3Mn octahedra,  a faceface with one O(4)Ba2Sm4 octahedra,  a faceface with one O(3)Ba4SmMn octahedra, and faces with two equivalent O(2)Ba2Sm3Mn octahedra. The corner-sharing octahedral tilt angles range from 0-76°. In the third O site, O(3) is bonded to four equivalent Ba(1), one Sm(2), and one Mn(1) atom to form distorted OBa4SmMn octahedra that share corners with two equivalent O(3)Ba4SmMn octahedra, corners with six equivalent O(2)Ba2Sm3Mn octahedra, edges with five equivalent O(3)Ba4SmMn octahedra, and faces with two equivalent O(2)Ba2Sm3Mn octahedra. The corner-sharing octahedral tilt angles range from 7-58°. In the fourth O site, O(4) is bonded to two equivalent Ba(2) and four equivalent Sm(1) atoms to form OBa2Sm4 octahedra that share corners with two equivalent O(4)Ba2Sm4 octahedra, corners with eight equivalent O(2)Ba2Sm3Mn octahedra, and faces with eight equivalent O(2)Ba2Sm3Mn octahedra. The corner-sharing octahedral tilt angles range from 0-61°.