MgMn4(Si4O11)2 crystallizes in the triclinic P-1 space group. Mg(1) is bonded in a 6-coordinate geometry to two equivalent O(6), two equivalent O(8), and two equivalent O(9) atoms. There are two inequivalent Mn sites. In the first Mn site, Mn(1) is bonded in a 5-coordinate geometry to one O(1), one O(11), one O(7), one O(8), and one O(9) atom. In the second Mn site, Mn(2) is bonded to one O(11), one O(3), one O(8), and two equivalent O(7) atoms to form distorted MnO5 square pyramids that share  a cornercorner with one Si(1)O4 tetrahedra,  a cornercorner with one Si(2)O4 tetrahedra,  a cornercorner with one Si(4)O4 tetrahedra, corners with two equivalent Si(3)O4 tetrahedra, and  an edgeedge with one Mn(2)O5 square pyramid. There are four inequivalent Si sites. In the first Si site, Si(1) is bonded to one O(1), one O(2), one O(3), and one O(4) atom to form SiO4 tetrahedra that share  a cornercorner with one Mn(2)O5 square pyramid,  a cornercorner with one Si(2)O4 tetrahedra, and  a cornercorner with one Si(3)O4 tetrahedra. In the second Si site, Si(2) is bonded to one O(10), one O(11), one O(4), and one O(5) atom to form SiO4 tetrahedra that share  a cornercorner with one Mn(2)O5 square pyramid,  a cornercorner with one Si(1)O4 tetrahedra,  a cornercorner with one Si(3)O4 tetrahedra, and  a cornercorner with one Si(4)O4 tetrahedra. In the third Si site, Si(3) is bonded to one O(2), one O(5), one O(6), and one O(7) atom to form SiO4 tetrahedra that share corners with two equivalent Mn(2)O5 square pyramids,  a cornercorner with one Si(1)O4 tetrahedra,  a cornercorner with one Si(2)O4 tetrahedra, and  a cornercorner with one Si(4)O4 tetrahedra. In the fourth Si site, Si(4) is bonded to one O(10), one O(6), one O(8), and one O(9) atom to form SiO4 tetrahedra that share  a cornercorner with one Mn(2)O5 square pyramid,  a cornercorner with one Si(2)O4 tetrahedra, and  a cornercorner with one Si(3)O4 tetrahedra. There are eleven inequivalent O sites. In the first O site, O(1) is bonded in a bent 150 degrees geometry to one Mn(1) and one Si(1) atom. In the second O site, O(2) is bonded in a distorted bent 150 degrees geometry to one Si(1) and one Si(3) atom. In the third O site, O(3) is bonded in a bent 120 degrees geometry to one Mn(2) and one Si(1) atom. In the fourth O site, O(4) is bonded in a bent 120 degrees geometry to one Si(1) and one Si(2) atom. In the fifth O site, O(5) is bonded in a bent 150 degrees geometry to one Si(2) and one Si(3) atom. In the sixth O site, O(6) is bonded in a 3-coordinate geometry to one Mg(1), one Si(3), and one Si(4) atom. In the seventh O site, O(7) is bonded in a distorted rectangular see-saw-like geometry to one Mn(1), two equivalent Mn(2), and one Si(3) atom. In the eighth O site, O(8) is bonded in a distorted rectangular see-saw-like geometry to one Mg(1), one Mn(1), one Mn(2), and one Si(4) atom. In the ninth O site, O(9) is bonded in a 3-coordinate geometry to one Mg(1), one Mn(1), and one Si(4) atom. In the tenth O site, O(10) is bonded in a distorted bent 150 degrees geometry to one Si(2) and one Si(4) atom. In the eleventh O site, O(11) is bonded in a 3-coordinate geometry to one Mn(1), one Mn(2), and one Si(2) atom.
MgMn4(Si4O11)2 crystallizes in the triclinic P-1 space group. Mg(1) is bonded in a 6-coordinate geometry to two equivalent O(6), two equivalent O(8), and two equivalent O(9) atoms. Both Mg(1)-O(6) bond lengths are 2.16 Å. Both Mg(1)-O(8) bond lengths are 2.42 Å. Both Mg(1)-O(9) bond lengths are 2.12 Å. There are two inequivalent Mn sites. In the first Mn site, Mn(1) is bonded in a 5-coordinate geometry to one O(1), one O(11), one O(7), one O(8), and one O(9) atom. The Mn(1)-O(1) bond length is 1.96 Å. The Mn(1)-O(11) bond length is 2.29 Å. The Mn(1)-O(7) bond length is 2.35 Å. The Mn(1)-O(8) bond length is 2.36 Å. The Mn(1)-O(9) bond length is 2.16 Å. In the second Mn site, Mn(2) is bonded to one O(11), one O(3), one O(8), and two equivalent O(7) atoms to form distorted MnO5 square pyramids that share  a cornercorner with one Si(1)O4 tetrahedra,  a cornercorner with one Si(2)O4 tetrahedra,  a cornercorner with one Si(4)O4 tetrahedra, corners with two equivalent Si(3)O4 tetrahedra, and  an edgeedge with one Mn(2)O5 square pyramid. The Mn(2)-O(11) bond length is 2.00 Å. The Mn(2)-O(3) bond length is 1.83 Å. The Mn(2)-O(8) bond length is 2.06 Å. There is one shorter (2.00 Å) and one longer (2.29 Å) Mn(2)-O(7) bond length. There are four inequivalent Si sites. In the first Si site, Si(1) is bonded to one O(1), one O(2), one O(3), and one O(4) atom to form SiO4 tetrahedra that share  a cornercorner with one Mn(2)O5 square pyramid,  a cornercorner with one Si(2)O4 tetrahedra, and  a cornercorner with one Si(3)O4 tetrahedra. The Si(1)-O(1) bond length is 1.58 Å. The Si(1)-O(2) bond length is 1.67 Å. The Si(1)-O(3) bond length is 1.65 Å. The Si(1)-O(4) bond length is 1.67 Å. In the second Si site, Si(2) is bonded to one O(10), one O(11), one O(4), and one O(5) atom to form SiO4 tetrahedra that share  a cornercorner with one Mn(2)O5 square pyramid,  a cornercorner with one Si(1)O4 tetrahedra,  a cornercorner with one Si(3)O4 tetrahedra, and  a cornercorner with one Si(4)O4 tetrahedra. The Si(2)-O(10) bond length is 1.67 Å. The Si(2)-O(11) bond length is 1.66 Å. The Si(2)-O(4) bond length is 1.61 Å. The Si(2)-O(5) bond length is 1.61 Å. In the third Si site, Si(3) is bonded to one O(2), one O(5), one O(6), and one O(7) atom to form SiO4 tetrahedra that share corners with two equivalent Mn(2)O5 square pyramids,  a cornercorner with one Si(1)O4 tetrahedra,  a cornercorner with one Si(2)O4 tetrahedra, and  a cornercorner with one Si(4)O4 tetrahedra. The Si(3)-O(2) bond length is 1.60 Å. The Si(3)-O(5) bond length is 1.61 Å. The Si(3)-O(6) bond length is 1.68 Å. The Si(3)-O(7) bond length is 1.67 Å. In the fourth Si site, Si(4) is bonded to one O(10), one O(6), one O(8), and one O(9) atom to form SiO4 tetrahedra that share  a cornercorner with one Mn(2)O5 square pyramid,  a cornercorner with one Si(2)O4 tetrahedra, and  a cornercorner with one Si(3)O4 tetrahedra. The Si(4)-O(10) bond length is 1.61 Å. The Si(4)-O(6) bond length is 1.69 Å. The Si(4)-O(8) bond length is 1.67 Å. The Si(4)-O(9) bond length is 1.63 Å. There are eleven inequivalent O sites. In the first O site, O(1) is bonded in a bent 150 degrees geometry to one Mn(1) and one Si(1) atom. In the second O site, O(2) is bonded in a distorted bent 150 degrees geometry to one Si(1) and one Si(3) atom. In the third O site, O(3) is bonded in a bent 120 degrees geometry to one Mn(2) and one Si(1) atom. In the fourth O site, O(4) is bonded in a bent 120 degrees geometry to one Si(1) and one Si(2) atom. In the fifth O site, O(5) is bonded in a bent 150 degrees geometry to one Si(2) and one Si(3) atom. In the sixth O site, O(6) is bonded in a 3-coordinate geometry to one Mg(1), one Si(3), and one Si(4) atom. In the seventh O site, O(7) is bonded in a distorted rectangular see-saw-like geometry to one Mn(1), two equivalent Mn(2), and one Si(3) atom. In the eighth O site, O(8) is bonded in a distorted rectangular see-saw-like geometry to one Mg(1), one Mn(1), one Mn(2), and one Si(4) atom. In the ninth O site, O(9) is bonded in a 3-coordinate geometry to one Mg(1), one Mn(1), and one Si(4) atom. In the tenth O site, O(10) is bonded in a distorted bent 150 degrees geometry to one Si(2) and one Si(4) atom. In the eleventh O site, O(11) is bonded in a 3-coordinate geometry to one Mn(1), one Mn(2), and one Si(2) atom.