Sr8MgMn6O20 crystallizes in the monoclinic C2/m space group. There are four inequivalent Sr sites. In the first Sr site, Sr(1) is bonded in a 9-coordinate geometry to one O(5), two equivalent O(1), two equivalent O(7), and four equivalent O(3) atoms. In the second Sr site, Sr(2) is bonded in a 9-coordinate geometry to one O(6), two equivalent O(1), two equivalent O(4), and four equivalent O(2) atoms. In the third Sr site, Sr(3) is bonded in a 9-coordinate geometry to one O(4), two equivalent O(1), two equivalent O(6), and four equivalent O(2) atoms. In the fourth Sr site, Sr(4) is bonded in a 4-coordinate geometry to one O(6), one O(7), two equivalent O(1), and two equivalent O(5) atoms. Mg(1) is bonded in a square co-planar geometry to four equivalent O(3) atoms. There are four inequivalent Mn sites. In the first Mn site, Mn(1) is bonded to one O(4), one O(6), two equivalent O(1), and two equivalent O(2) atoms to form a mixture of distorted corner and face-sharing MnO6 octahedra. The corner-sharing octahedral tilt angles are 14°. In the second Mn site, Mn(2) is bonded to one O(5), one O(7), two equivalent O(1), and two equivalent O(3) atoms to form a mixture of distorted corner and face-sharing MnO6 octahedra. The corner-sharing octahedral tilt angles are 14°. In the third Mn site, Mn(3) is bonded to two equivalent O(6) and four equivalent O(2) atoms to form face-sharing MnO6 octahedra. In the fourth Mn site, Mn(4) is bonded to two equivalent O(5) and four equivalent O(3) atoms to form face-sharing MnO6 octahedra. There are seven inequivalent O sites. In the first O site, O(2) is bonded in a 6-coordinate geometry to two equivalent Sr(2), two equivalent Sr(3), one Mn(1), and one Mn(3) atom. In the second O site, O(3) is bonded in a 4-coordinate geometry to two equivalent Sr(1), one Mg(1), one Mn(2), and one Mn(4) atom. In the third O site, O(4) is bonded in a 2-coordinate geometry to one Sr(3), two equivalent Sr(2), and one Mn(1) atom. In the fourth O site, O(5) is bonded in a 5-coordinate geometry to one Sr(1), two equivalent Sr(4), one Mn(2), and one Mn(4) atom. In the fifth O site, O(6) is bonded to one Sr(2), one Sr(4), two equivalent Sr(3), one Mn(1), and one Mn(3) atom to form distorted corner-sharing OSr4Mn2 octahedra. The corner-sharing octahedral tilt angles range from 0-7°. In the sixth O site, O(7) is bonded in a 4-coordinate geometry to one Sr(4), two equivalent Sr(1), and one Mn(2) atom. In the seventh O site, O(1) is bonded in a 2-coordinate geometry to one Sr(1), one Sr(2), one Sr(3), one Sr(4), one Mn(1), and one Mn(2) atom.
Sr8MgMn6O20 crystallizes in the monoclinic C2/m space group. There are four inequivalent Sr sites. In the first Sr site, Sr(1) is bonded in a 9-coordinate geometry to one O(5), two equivalent O(1), two equivalent O(7), and four equivalent O(3) atoms. The Sr(1)-O(5) bond length is 2.51 Å. Both Sr(1)-O(1) bond lengths are 3.16 Å. Both Sr(1)-O(7) bond lengths are 2.86 Å. There are two shorter (2.60 Å) and two longer (3.02 Å) Sr(1)-O(3) bond lengths. In the second Sr site, Sr(2) is bonded in a 9-coordinate geometry to one O(6), two equivalent O(1), two equivalent O(4), and four equivalent O(2) atoms. The Sr(2)-O(6) bond length is 2.53 Å. Both Sr(2)-O(1) bond lengths are 2.99 Å. Both Sr(2)-O(4) bond lengths are 2.87 Å. There are two shorter (2.53 Å) and two longer (2.81 Å) Sr(2)-O(2) bond lengths. In the third Sr site, Sr(3) is bonded in a 9-coordinate geometry to one O(4), two equivalent O(1), two equivalent O(6), and four equivalent O(2) atoms. The Sr(3)-O(4) bond length is 2.40 Å. Both Sr(3)-O(1) bond lengths are 2.70 Å. Both Sr(3)-O(6) bond lengths are 2.78 Å. There are two shorter (2.61 Å) and two longer (2.89 Å) Sr(3)-O(2) bond lengths. In the fourth Sr site, Sr(4) is bonded in a 4-coordinate geometry to one O(6), one O(7), two equivalent O(1), and two equivalent O(5) atoms. The Sr(4)-O(6) bond length is 2.38 Å. The Sr(4)-O(7) bond length is 2.34 Å. Both Sr(4)-O(1) bond lengths are 2.50 Å. Both Sr(4)-O(5) bond lengths are 2.90 Å. Mg(1) is bonded in a square co-planar geometry to four equivalent O(3) atoms. All Mg(1)-O(3) bond lengths are 1.98 Å. There are four inequivalent Mn sites. In the first Mn site, Mn(1) is bonded to one O(4), one O(6), two equivalent O(1), and two equivalent O(2) atoms to form a mixture of distorted corner and face-sharing MnO6 octahedra. The corner-sharing octahedral tilt angles are 14°. The Mn(1)-O(4) bond length is 1.82 Å. The Mn(1)-O(6) bond length is 2.16 Å. Both Mn(1)-O(1) bond lengths are 1.88 Å. Both Mn(1)-O(2) bond lengths are 2.05 Å. In the second Mn site, Mn(2) is bonded to one O(5), one O(7), two equivalent O(1), and two equivalent O(3) atoms to form a mixture of distorted corner and face-sharing MnO6 octahedra. The corner-sharing octahedral tilt angles are 14°. The Mn(2)-O(5) bond length is 2.05 Å. The Mn(2)-O(7) bond length is 1.84 Å. Both Mn(2)-O(1) bond lengths are 1.99 Å. Both Mn(2)-O(3) bond lengths are 2.21 Å. In the third Mn site, Mn(3) is bonded to two equivalent O(6) and four equivalent O(2) atoms to form face-sharing MnO6 octahedra. Both Mn(3)-O(6) bond lengths are 1.92 Å. All Mn(3)-O(2) bond lengths are 1.93 Å. In the fourth Mn site, Mn(4) is bonded to two equivalent O(5) and four equivalent O(3) atoms to form face-sharing MnO6 octahedra. Both Mn(4)-O(5) bond lengths are 2.00 Å. All Mn(4)-O(3) bond lengths are 1.93 Å. There are seven inequivalent O sites. In the first O site, O(2) is bonded in a 6-coordinate geometry to two equivalent Sr(2), two equivalent Sr(3), one Mn(1), and one Mn(3) atom. In the second O site, O(3) is bonded in a 4-coordinate geometry to two equivalent Sr(1), one Mg(1), one Mn(2), and one Mn(4) atom. In the third O site, O(4) is bonded in a 2-coordinate geometry to one Sr(3), two equivalent Sr(2), and one Mn(1) atom. In the fourth O site, O(5) is bonded in a 5-coordinate geometry to one Sr(1), two equivalent Sr(4), one Mn(2), and one Mn(4) atom. In the fifth O site, O(6) is bonded to one Sr(2), one Sr(4), two equivalent Sr(3), one Mn(1), and one Mn(3) atom to form distorted corner-sharing OSr4Mn2 octahedra. The corner-sharing octahedral tilt angles range from 0-7°. In the sixth O site, O(7) is bonded in a 4-coordinate geometry to one Sr(4), two equivalent Sr(1), and one Mn(2) atom. In the seventh O site, O(1) is bonded in a 2-coordinate geometry to one Sr(1), one Sr(2), one Sr(3), one Sr(4), one Mn(1), and one Mn(2) atom.