Ca4Mn4O11 crystallizes in the tetragonal P4/mmm space group. There are two inequivalent Ca sites. In the first Ca site, Ca(1) is bonded in a distorted q6 geometry to two equivalent O(2) and eight equivalent O(4) atoms. In the second Ca site, Ca(2) is bonded to two equivalent O(1), two equivalent O(3), and eight equivalent O(4) atoms to form CaO12 cuboctahedra that share corners with four equivalent Ca(2)O12 cuboctahedra, faces with four equivalent Ca(2)O12 cuboctahedra, faces with four equivalent Mn(2)O6 octahedra, and faces with four equivalent Mn(1)O5 square pyramids. There are two inequivalent Mn sites. In the first Mn site, Mn(1) is bonded to one O(1) and four equivalent O(4) atoms to form MnO5 square pyramids that share corners with four equivalent Mn(2)O6 octahedra,  a cornercorner with one Mn(1)O5 square pyramid, and faces with four equivalent Ca(2)O12 cuboctahedra. The corner-sharing octahedral tilt angles are 10°. In the second Mn site, Mn(2) is bonded to one O(2), one O(3), and four equivalent O(4) atoms to form MnO6 octahedra that share corners with two equivalent Mn(2)O6 octahedra, corners with four equivalent Mn(1)O5 square pyramids, and faces with four equivalent Ca(2)O12 cuboctahedra. The corner-sharing octahedra are not tilted. There are four inequivalent O sites. In the first O site, O(1) is bonded in a distorted linear geometry to four equivalent Ca(2) and two equivalent Mn(1) atoms. In the second O site, O(2) is bonded in a linear geometry to four equivalent Ca(1) and two equivalent Mn(2) atoms. In the third O site, O(3) is bonded to four equivalent Ca(2) and two equivalent Mn(2) atoms to form distorted corner-sharing OCa4Mn2 octahedra. The corner-sharing octahedra are not tilted. In the fourth O site, O(4) is bonded in a 6-coordinate geometry to two equivalent Ca(1), two equivalent Ca(2), one Mn(1), and one Mn(2) atom.
Ca4Mn4O11 crystallizes in the tetragonal P4/mmm space group. There are two inequivalent Ca sites. In the first Ca site, Ca(1) is bonded in a distorted q6 geometry to two equivalent O(2) and eight equivalent O(4) atoms. Both Ca(1)-O(2) bond lengths are 2.72 Å. All Ca(1)-O(4) bond lengths are 2.59 Å. In the second Ca site, Ca(2) is bonded to two equivalent O(1), two equivalent O(3), and eight equivalent O(4) atoms to form CaO12 cuboctahedra that share corners with four equivalent Ca(2)O12 cuboctahedra, faces with four equivalent Ca(2)O12 cuboctahedra, faces with four equivalent Mn(2)O6 octahedra, and faces with four equivalent Mn(1)O5 square pyramids. Both Ca(2)-O(1) bond lengths are 2.72 Å. Both Ca(2)-O(3) bond lengths are 2.72 Å. All Ca(2)-O(4) bond lengths are 2.83 Å. There are two inequivalent Mn sites. In the first Mn site, Mn(1) is bonded to one O(1) and four equivalent O(4) atoms to form MnO5 square pyramids that share corners with four equivalent Mn(2)O6 octahedra,  a cornercorner with one Mn(1)O5 square pyramid, and faces with four equivalent Ca(2)O12 cuboctahedra. The corner-sharing octahedral tilt angles are 10°. The Mn(1)-O(1) bond length is 1.87 Å. All Mn(1)-O(4) bond lengths are 1.90 Å. In the second Mn site, Mn(2) is bonded to one O(2), one O(3), and four equivalent O(4) atoms to form MnO6 octahedra that share corners with two equivalent Mn(2)O6 octahedra, corners with four equivalent Mn(1)O5 square pyramids, and faces with four equivalent Ca(2)O12 cuboctahedra. The corner-sharing octahedra are not tilted. The Mn(2)-O(2) bond length is 1.85 Å. The Mn(2)-O(3) bond length is 1.96 Å. All Mn(2)-O(4) bond lengths are 1.96 Å. There are four inequivalent O sites. In the first O site, O(1) is bonded in a distorted linear geometry to four equivalent Ca(2) and two equivalent Mn(1) atoms. In the second O site, O(2) is bonded in a linear geometry to four equivalent Ca(1) and two equivalent Mn(2) atoms. In the third O site, O(3) is bonded to four equivalent Ca(2) and two equivalent Mn(2) atoms to form distorted corner-sharing OCa4Mn2 octahedra. The corner-sharing octahedra are not tilted. In the fourth O site, O(4) is bonded in a 6-coordinate geometry to two equivalent Ca(1), two equivalent Ca(2), one Mn(1), and one Mn(2) atom.