Sr3MgMn4O12 crystallizes in the triclinic P1 space group. There are three inequivalent Sr sites. In the first Sr site, Sr(1) is bonded in a 9-coordinate geometry to one O(1), one O(10), one O(2), one O(3), one O(4), one O(5), one O(8), and two equivalent O(7) atoms. In the second Sr site, Sr(2) is bonded in a 5-coordinate geometry to one O(10), one O(12), one O(6), one O(8), and one O(9) atom. In the third Sr site, Sr(3) is bonded in a 9-coordinate geometry to one O(12), one O(7), one O(9), two equivalent O(2), two equivalent O(4), and two equivalent O(5) atoms. Mg(1) is bonded to one O(1), one O(10), one O(3), one O(7), and one O(8) atom to form MgO5 square pyramids that share corners with two equivalent Mn(3)O6 octahedra,  an edgeedge with one Mn(4)O6 octahedra,  a faceface with one Mn(2)O6 octahedra, and  a faceface with one Mn(3)O6 octahedra. The corner-sharing octahedral tilt angles are 50°. There are four inequivalent Mn sites. In the first Mn site, Mn(1) is bonded to one O(12), one O(2), one O(4), one O(5), one O(6), and one O(9) atom to form a mixture of distorted corner and face-sharing MnO6 octahedra. The corner-sharing octahedral tilt angles range from 21-26°. In the second Mn site, Mn(2) is bonded to one O(1), one O(2), one O(3), one O(4), one O(5), and one O(7) atom to form MnO6 octahedra that share corners with three equivalent Mn(3)O6 octahedra,  a faceface with one Mn(1)O6 octahedra, and  a faceface with one Mg(1)O5 square pyramid. The corner-sharing octahedral tilt angles range from 25-29°. In the third Mn site, Mn(3) is bonded to one O(1), one O(10), one O(11), one O(3), one O(7), and one O(8) atom to form MnO6 octahedra that share corners with three equivalent Mn(2)O6 octahedra, corners with two equivalent Mg(1)O5 square pyramids,  a faceface with one Mn(4)O6 octahedra, and  a faceface with one Mg(1)O5 square pyramid. The corner-sharing octahedral tilt angles range from 25-29°. In the fourth Mn site, Mn(4) is bonded to one O(10), one O(11), one O(12), one O(6), one O(8), and one O(9) atom to form MnO6 octahedra that share corners with three equivalent Mn(1)O6 octahedra,  an edgeedge with one Mg(1)O5 square pyramid, and  a faceface with one Mn(3)O6 octahedra. The corner-sharing octahedral tilt angles range from 21-26°. There are twelve inequivalent O sites. In the first O site, O(1) is bonded in a distorted rectangular see-saw-like geometry to one Sr(1), one Mg(1), one Mn(2), and one Mn(3) atom. In the second O site, O(2) is bonded in a 5-coordinate geometry to one Sr(1), two equivalent Sr(3), one Mn(1), and one Mn(2) atom. In the third O site, O(3) is bonded in a 4-coordinate geometry to one Sr(1), one Mg(1), one Mn(2), and one Mn(3) atom. In the fourth O site, O(4) is bonded in a distorted L-shaped geometry to one Sr(1), two equivalent Sr(3), one Mn(1), and one Mn(2) atom. In the fifth O site, O(5) is bonded in a distorted L-shaped geometry to one Sr(1), two equivalent Sr(3), one Mn(1), and one Mn(2) atom. In the sixth O site, O(6) is bonded in a 3-coordinate geometry to one Sr(2), one Mn(1), and one Mn(4) atom. In the seventh O site, O(7) is bonded in a 6-coordinate geometry to one Sr(3), two equivalent Sr(1), one Mg(1), one Mn(2), and one Mn(3) atom. In the eighth O site, O(8) is bonded in a 5-coordinate geometry to one Sr(1), one Sr(2), one Mg(1), one Mn(3), and one Mn(4) atom. In the ninth O site, O(9) is bonded in a rectangular see-saw-like geometry to one Sr(2), one Sr(3), one Mn(1), and one Mn(4) atom. In the tenth O site, O(10) is bonded in a 5-coordinate geometry to one Sr(1), one Sr(2), one Mg(1), one Mn(3), and one Mn(4) atom. In the eleventh O site, O(11) is bonded in a distorted L-shaped geometry to one Mn(3) and one Mn(4) atom. In the twelfth O site, O(12) is bonded in a rectangular see-saw-like geometry to one Sr(2), one Sr(3), one Mn(1), and one Mn(4) atom.
Sr3MgMn4O12 crystallizes in the triclinic P1 space group. There are three inequivalent Sr sites. In the first Sr site, Sr(1) is bonded in a 9-coordinate geometry to one O(1), one O(10), one O(2), one O(3), one O(4), one O(5), one O(8), and two equivalent O(7) atoms. The Sr(1)-O(1) bond length is 2.61 Å. The Sr(1)-O(10) bond length is 2.95 Å. The Sr(1)-O(2) bond length is 2.46 Å. The Sr(1)-O(3) bond length is 2.62 Å. The Sr(1)-O(4) bond length is 2.81 Å. The Sr(1)-O(5) bond length is 2.80 Å. The Sr(1)-O(8) bond length is 2.96 Å. Both Sr(1)-O(7) bond lengths are 2.81 Å. In the second Sr site, Sr(2) is bonded in a 5-coordinate geometry to one O(10), one O(12), one O(6), one O(8), and one O(9) atom. The Sr(2)-O(10) bond length is 2.36 Å. The Sr(2)-O(12) bond length is 2.42 Å. The Sr(2)-O(6) bond length is 2.51 Å. The Sr(2)-O(8) bond length is 2.36 Å. The Sr(2)-O(9) bond length is 2.42 Å. In the third Sr site, Sr(3) is bonded in a 9-coordinate geometry to one O(12), one O(7), one O(9), two equivalent O(2), two equivalent O(4), and two equivalent O(5) atoms. The Sr(3)-O(12) bond length is 2.49 Å. The Sr(3)-O(7) bond length is 2.51 Å. The Sr(3)-O(9) bond length is 2.49 Å. There is one shorter (2.84 Å) and one longer (2.85 Å) Sr(3)-O(2) bond length. There is one shorter (2.82 Å) and one longer (2.87 Å) Sr(3)-O(4) bond length. There is one shorter (2.81 Å) and one longer (2.88 Å) Sr(3)-O(5) bond length. Mg(1) is bonded to one O(1), one O(10), one O(3), one O(7), and one O(8) atom to form MgO5 square pyramids that share corners with two equivalent Mn(3)O6 octahedra,  an edgeedge with one Mn(4)O6 octahedra,  a faceface with one Mn(2)O6 octahedra, and  a faceface with one Mn(3)O6 octahedra. The corner-sharing octahedral tilt angles are 50°. The Mg(1)-O(1) bond length is 2.05 Å. The Mg(1)-O(10) bond length is 1.98 Å. The Mg(1)-O(3) bond length is 2.05 Å. The Mg(1)-O(7) bond length is 1.99 Å. The Mg(1)-O(8) bond length is 1.97 Å. There are four inequivalent Mn sites. In the first Mn site, Mn(1) is bonded to one O(12), one O(2), one O(4), one O(5), one O(6), and one O(9) atom to form a mixture of distorted corner and face-sharing MnO6 octahedra. The corner-sharing octahedral tilt angles range from 21-26°. The Mn(1)-O(12) bond length is 2.03 Å. The Mn(1)-O(2) bond length is 2.11 Å. The Mn(1)-O(4) bond length is 1.95 Å. The Mn(1)-O(5) bond length is 1.95 Å. The Mn(1)-O(6) bond length is 1.88 Å. The Mn(1)-O(9) bond length is 2.03 Å. In the second Mn site, Mn(2) is bonded to one O(1), one O(2), one O(3), one O(4), one O(5), and one O(7) atom to form MnO6 octahedra that share corners with three equivalent Mn(3)O6 octahedra,  a faceface with one Mn(1)O6 octahedra, and  a faceface with one Mg(1)O5 square pyramid. The corner-sharing octahedral tilt angles range from 25-29°. The Mn(2)-O(1) bond length is 2.05 Å. The Mn(2)-O(2) bond length is 1.85 Å. The Mn(2)-O(3) bond length is 2.05 Å. The Mn(2)-O(4) bond length is 1.89 Å. The Mn(2)-O(5) bond length is 1.88 Å. The Mn(2)-O(7) bond length is 2.11 Å. In the third Mn site, Mn(3) is bonded to one O(1), one O(10), one O(11), one O(3), one O(7), and one O(8) atom to form MnO6 octahedra that share corners with three equivalent Mn(2)O6 octahedra, corners with two equivalent Mg(1)O5 square pyramids,  a faceface with one Mn(4)O6 octahedra, and  a faceface with one Mg(1)O5 square pyramid. The corner-sharing octahedral tilt angles range from 25-29°. The Mn(3)-O(1) bond length is 1.99 Å. The Mn(3)-O(10) bond length is 1.97 Å. The Mn(3)-O(11) bond length is 1.87 Å. The Mn(3)-O(3) bond length is 1.99 Å. The Mn(3)-O(7) bond length is 2.07 Å. The Mn(3)-O(8) bond length is 1.97 Å. In the fourth Mn site, Mn(4) is bonded to one O(10), one O(11), one O(12), one O(6), one O(8), and one O(9) atom to form MnO6 octahedra that share corners with three equivalent Mn(1)O6 octahedra,  an edgeedge with one Mg(1)O5 square pyramid, and  a faceface with one Mn(3)O6 octahedra. The corner-sharing octahedral tilt angles range from 21-26°. The Mn(4)-O(10) bond length is 2.16 Å. The Mn(4)-O(11) bond length is 1.92 Å. The Mn(4)-O(12) bond length is 1.90 Å. The Mn(4)-O(6) bond length is 2.00 Å. The Mn(4)-O(8) bond length is 2.15 Å. The Mn(4)-O(9) bond length is 1.90 Å. There are twelve inequivalent O sites. In the first O site, O(1) is bonded in a distorted rectangular see-saw-like geometry to one Sr(1), one Mg(1), one Mn(2), and one Mn(3) atom. In the second O site, O(2) is bonded in a 5-coordinate geometry to one Sr(1), two equivalent Sr(3), one Mn(1), and one Mn(2) atom. In the third O site, O(3) is bonded in a 4-coordinate geometry to one Sr(1), one Mg(1), one Mn(2), and one Mn(3) atom. In the fourth O site, O(4) is bonded in a distorted L-shaped geometry to one Sr(1), two equivalent Sr(3), one Mn(1), and one Mn(2) atom. In the fifth O site, O(5) is bonded in a distorted L-shaped geometry to one Sr(1), two equivalent Sr(3), one Mn(1), and one Mn(2) atom. In the sixth O site, O(6) is bonded in a 3-coordinate geometry to one Sr(2), one Mn(1), and one Mn(4) atom. In the seventh O site, O(7) is bonded in a 6-coordinate geometry to one Sr(3), two equivalent Sr(1), one Mg(1), one Mn(2), and one Mn(3) atom. In the eighth O site, O(8) is bonded in a 5-coordinate geometry to one Sr(1), one Sr(2), one Mg(1), one Mn(3), and one Mn(4) atom. In the ninth O site, O(9) is bonded in a rectangular see-saw-like geometry to one Sr(2), one Sr(3), one Mn(1), and one Mn(4) atom. In the tenth O site, O(10) is bonded in a 5-coordinate geometry to one Sr(1), one Sr(2), one Mg(1), one Mn(3), and one Mn(4) atom. In the eleventh O site, O(11) is bonded in a distorted L-shaped geometry to one Mn(3) and one Mn(4) atom. In the twelfth O site, O(12) is bonded in a rectangular see-saw-like geometry to one Sr(2), one Sr(3), one Mn(1), and one Mn(4) atom.