Ba7Ca2Mn5O20 crystallizes in the trigonal R-3m space group. There are four inequivalent Ba sites. In the first Ba site, Ba(1) is bonded to three equivalent O(1) and nine equivalent O(3) atoms to form BaO12 cuboctahedra that share corners with six equivalent Ba(1)O12 cuboctahedra, corners with three equivalent Mn(2)O6 octahedra, faces with three equivalent Ba(1)O12 cuboctahedra,  a faceface with one Ca(1)O6 octahedra, faces with three equivalent Mn(2)O6 octahedra, and faces with three equivalent Mn(3)O6 octahedra. The corner-sharing octahedral tilt angles are 8°. In the second Ba site, Ba(2) is bonded to six equivalent O(2) atoms to form distorted BaO6 cuboctahedra that share corners with six equivalent Mn(1)O4 tetrahedra and faces with two equivalent Ca(1)O6 octahedra. In the third Ba site, Ba(3) is bonded in a 10-coordinate geometry to one O(4), three equivalent O(1), and six equivalent O(2) atoms. In the fourth Ba site, Ba(4) is bonded in a 9-coordinate geometry to three equivalent O(3) and six equivalent O(1) atoms. Ca(1) is bonded to three equivalent O(1) and three equivalent O(2) atoms to form CaO6 octahedra that share corners with three equivalent Mn(2)O6 octahedra, corners with three equivalent Mn(1)O4 tetrahedra,  a faceface with one Ba(1)O12 cuboctahedra, and  a faceface with one Ba(2)O6 cuboctahedra. The corner-sharing octahedral tilt angles are 1°. There are three inequivalent Mn sites. In the first Mn site, Mn(1) is bonded to one O(4) and three equivalent O(2) atoms to form MnO4 tetrahedra that share corners with three equivalent Ba(2)O6 cuboctahedra and corners with three equivalent Ca(1)O6 octahedra. The corner-sharing octahedral tilt angles are 23°. In the second Mn site, Mn(2) is bonded to three equivalent O(1) and three equivalent O(3) atoms to form MnO6 octahedra that share corners with three equivalent Ba(1)O12 cuboctahedra, corners with three equivalent Ca(1)O6 octahedra, faces with three equivalent Ba(1)O12 cuboctahedra, and  a faceface with one Mn(3)O6 octahedra. The corner-sharing octahedral tilt angles are 1°. In the third Mn site, Mn(3) is bonded to six equivalent O(3) atoms to form MnO6 octahedra that share faces with six equivalent Ba(1)O12 cuboctahedra and faces with two equivalent Mn(2)O6 octahedra. There are four inequivalent O sites. In the first O site, O(1) is bonded in a 2-coordinate geometry to one Ba(1), one Ba(3), two equivalent Ba(4), one Ca(1), and one Mn(2) atom. In the second O site, O(2) is bonded in a 5-coordinate geometry to one Ba(2), two equivalent Ba(3), one Ca(1), and one Mn(1) atom. In the third O site, O(3) is bonded in a 6-coordinate geometry to one Ba(4), three equivalent Ba(1), one Mn(2), and one Mn(3) atom. In the fourth O site, O(4) is bonded in a distorted single-bond geometry to one Ba(3) and one Mn(1) atom.
Ba7Ca2Mn5O20 crystallizes in the trigonal R-3m space group. There are four inequivalent Ba sites. In the first Ba site, Ba(1) is bonded to three equivalent O(1) and nine equivalent O(3) atoms to form BaO12 cuboctahedra that share corners with six equivalent Ba(1)O12 cuboctahedra, corners with three equivalent Mn(2)O6 octahedra, faces with three equivalent Ba(1)O12 cuboctahedra,  a faceface with one Ca(1)O6 octahedra, faces with three equivalent Mn(2)O6 octahedra, and faces with three equivalent Mn(3)O6 octahedra. The corner-sharing octahedral tilt angles are 8°. All Ba(1)-O(1) bond lengths are 3.13 Å. There are six shorter (2.96 Å) and three longer (3.01 Å) Ba(1)-O(3) bond lengths. In the second Ba site, Ba(2) is bonded to six equivalent O(2) atoms to form distorted BaO6 cuboctahedra that share corners with six equivalent Mn(1)O4 tetrahedra and faces with two equivalent Ca(1)O6 octahedra. All Ba(2)-O(2) bond lengths are 2.84 Å. In the third Ba site, Ba(3) is bonded in a 10-coordinate geometry to one O(4), three equivalent O(1), and six equivalent O(2) atoms. The Ba(3)-O(4) bond length is 2.75 Å. All Ba(3)-O(1) bond lengths are 2.73 Å. All Ba(3)-O(2) bond lengths are 3.02 Å. In the fourth Ba site, Ba(4) is bonded in a 9-coordinate geometry to three equivalent O(3) and six equivalent O(1) atoms. All Ba(4)-O(3) bond lengths are 2.71 Å. All Ba(4)-O(1) bond lengths are 3.00 Å. Ca(1) is bonded to three equivalent O(1) and three equivalent O(2) atoms to form CaO6 octahedra that share corners with three equivalent Mn(2)O6 octahedra, corners with three equivalent Mn(1)O4 tetrahedra,  a faceface with one Ba(1)O12 cuboctahedra, and  a faceface with one Ba(2)O6 cuboctahedra. The corner-sharing octahedral tilt angles are 1°. All Ca(1)-O(1) bond lengths are 2.19 Å. All Ca(1)-O(2) bond lengths are 2.46 Å. There are three inequivalent Mn sites. In the first Mn site, Mn(1) is bonded to one O(4) and three equivalent O(2) atoms to form MnO4 tetrahedra that share corners with three equivalent Ba(2)O6 cuboctahedra and corners with three equivalent Ca(1)O6 octahedra. The corner-sharing octahedral tilt angles are 23°. The Mn(1)-O(4) bond length is 1.69 Å. All Mn(1)-O(2) bond lengths are 1.73 Å. In the second Mn site, Mn(2) is bonded to three equivalent O(1) and three equivalent O(3) atoms to form MnO6 octahedra that share corners with three equivalent Ba(1)O12 cuboctahedra, corners with three equivalent Ca(1)O6 octahedra, faces with three equivalent Ba(1)O12 cuboctahedra, and  a faceface with one Mn(3)O6 octahedra. The corner-sharing octahedral tilt angles are 1°. All Mn(2)-O(1) bond lengths are 1.88 Å. All Mn(2)-O(3) bond lengths are 2.02 Å. In the third Mn site, Mn(3) is bonded to six equivalent O(3) atoms to form MnO6 octahedra that share faces with six equivalent Ba(1)O12 cuboctahedra and faces with two equivalent Mn(2)O6 octahedra. All Mn(3)-O(3) bond lengths are 1.94 Å. There are four inequivalent O sites. In the first O site, O(1) is bonded in a 2-coordinate geometry to one Ba(1), one Ba(3), two equivalent Ba(4), one Ca(1), and one Mn(2) atom. In the second O site, O(2) is bonded in a 5-coordinate geometry to one Ba(2), two equivalent Ba(3), one Ca(1), and one Mn(1) atom. In the third O site, O(3) is bonded in a 6-coordinate geometry to one Ba(4), three equivalent Ba(1), one Mn(2), and one Mn(3) atom. In the fourth O site, O(4) is bonded in a distorted single-bond geometry to one Ba(3) and one Mn(1) atom.