La4Mn5(Si2O11)2 crystallizes in the monoclinic C2/m space group. There are two inequivalent La sites. In the first La site, La(1) is bonded in a 7-coordinate geometry to one O(8), two equivalent O(1), two equivalent O(2), and two equivalent O(3) atoms. In the second La site, La(2) is bonded in a 10-coordinate geometry to one O(4), one O(8), two equivalent O(1), two equivalent O(2), two equivalent O(3), and two equivalent O(6) atoms. There are three inequivalent Mn sites. In the first Mn site, Mn(1) is bonded to two equivalent O(1), two equivalent O(4), and two equivalent O(5) atoms to form MnO6 octahedra that share corners with four equivalent Mn(2)O6 octahedra, corners with two equivalent Si(2)O4 tetrahedra, and edges with two equivalent Mn(1)O6 octahedra. The corner-sharing octahedral tilt angles range from 48-49°. In the second Mn site, Mn(2) is bonded to one O(4), one O(5), and four equivalent O(2) atoms to form a mixture of distorted corner and edge-sharing MnO6 octahedra. The corner-sharing octahedral tilt angles range from 48-49°. In the third Mn site, Mn(3) is bonded to two equivalent O(6) and four equivalent O(3) atoms to form MnO6 octahedra that share corners with two equivalent Si(2)O4 tetrahedra and corners with four equivalent Si(1)O4 tetrahedra. There are two inequivalent Si sites. In the first Si site, Si(1) is bonded to one O(7), one O(8), and two equivalent O(3) atoms to form SiO4 tetrahedra that share corners with two equivalent Mn(3)O6 octahedra and  a cornercorner with one Si(2)O4 tetrahedra. The corner-sharing octahedral tilt angles are 48°. In the second Si site, Si(2) is bonded to one O(6), one O(7), and two equivalent O(1) atoms to form SiO4 tetrahedra that share  a cornercorner with one Mn(3)O6 octahedra, corners with two equivalent Mn(1)O6 octahedra, and  a cornercorner with one Si(1)O4 tetrahedra. The corner-sharing octahedral tilt angles range from 41-58°. There are eight inequivalent O sites. In the first O site, O(3) is bonded in a 4-coordinate geometry to one La(1), one La(2), one Mn(3), and one Si(1) atom. In the second O site, O(4) is bonded in a 2-coordinate geometry to one La(2), one Mn(2), and two equivalent Mn(1) atoms. In the third O site, O(5) is bonded in a distorted trigonal planar geometry to one Mn(2) and two equivalent Mn(1) atoms. In the fourth O site, O(6) is bonded in a 2-coordinate geometry to two equivalent La(2), one Mn(3), and one Si(2) atom. In the fifth O site, O(7) is bonded in a linear geometry to one Si(1) and one Si(2) atom. In the sixth O site, O(8) is bonded in a 3-coordinate geometry to one La(1), one La(2), and one Si(1) atom. In the seventh O site, O(1) is bonded in a 4-coordinate geometry to one La(1), one La(2), one Mn(1), and one Si(2) atom. In the eighth O site, O(2) is bonded in a distorted see-saw-like geometry to one La(1), one La(2), and two equivalent Mn(2) atoms.
La4Mn5(Si2O11)2 crystallizes in the monoclinic C2/m space group. There are two inequivalent La sites. In the first La site, La(1) is bonded in a 7-coordinate geometry to one O(8), two equivalent O(1), two equivalent O(2), and two equivalent O(3) atoms. The La(1)-O(8) bond length is 2.63 Å. Both La(1)-O(1) bond lengths are 2.56 Å. Both La(1)-O(2) bond lengths are 2.48 Å. Both La(1)-O(3) bond lengths are 2.50 Å. In the second La site, La(2) is bonded in a 10-coordinate geometry to one O(4), one O(8), two equivalent O(1), two equivalent O(2), two equivalent O(3), and two equivalent O(6) atoms. The La(2)-O(4) bond length is 2.66 Å. The La(2)-O(8) bond length is 2.51 Å. Both La(2)-O(1) bond lengths are 2.68 Å. Both La(2)-O(2) bond lengths are 2.55 Å. Both La(2)-O(3) bond lengths are 2.68 Å. Both La(2)-O(6) bond lengths are 2.97 Å. There are three inequivalent Mn sites. In the first Mn site, Mn(1) is bonded to two equivalent O(1), two equivalent O(4), and two equivalent O(5) atoms to form MnO6 octahedra that share corners with four equivalent Mn(2)O6 octahedra, corners with two equivalent Si(2)O4 tetrahedra, and edges with two equivalent Mn(1)O6 octahedra. The corner-sharing octahedral tilt angles range from 48-49°. Both Mn(1)-O(1) bond lengths are 1.96 Å. Both Mn(1)-O(4) bond lengths are 1.94 Å. Both Mn(1)-O(5) bond lengths are 1.90 Å. In the second Mn site, Mn(2) is bonded to one O(4), one O(5), and four equivalent O(2) atoms to form a mixture of distorted corner and edge-sharing MnO6 octahedra. The corner-sharing octahedral tilt angles range from 48-49°. The Mn(2)-O(4) bond length is 2.48 Å. The Mn(2)-O(5) bond length is 2.04 Å. All Mn(2)-O(2) bond lengths are 1.97 Å. In the third Mn site, Mn(3) is bonded to two equivalent O(6) and four equivalent O(3) atoms to form MnO6 octahedra that share corners with two equivalent Si(2)O4 tetrahedra and corners with four equivalent Si(1)O4 tetrahedra. Both Mn(3)-O(6) bond lengths are 2.12 Å. All Mn(3)-O(3) bond lengths are 2.25 Å. There are two inequivalent Si sites. In the first Si site, Si(1) is bonded to one O(7), one O(8), and two equivalent O(3) atoms to form SiO4 tetrahedra that share corners with two equivalent Mn(3)O6 octahedra and  a cornercorner with one Si(2)O4 tetrahedra. The corner-sharing octahedral tilt angles are 48°. The Si(1)-O(7) bond length is 1.66 Å. The Si(1)-O(8) bond length is 1.61 Å. Both Si(1)-O(3) bond lengths are 1.65 Å. In the second Si site, Si(2) is bonded to one O(6), one O(7), and two equivalent O(1) atoms to form SiO4 tetrahedra that share  a cornercorner with one Mn(3)O6 octahedra, corners with two equivalent Mn(1)O6 octahedra, and  a cornercorner with one Si(1)O4 tetrahedra. The corner-sharing octahedral tilt angles range from 41-58°. The Si(2)-O(6) bond length is 1.60 Å. The Si(2)-O(7) bond length is 1.64 Å. Both Si(2)-O(1) bond lengths are 1.67 Å. There are eight inequivalent O sites. In the first O site, O(3) is bonded in a 4-coordinate geometry to one La(1), one La(2), one Mn(3), and one Si(1) atom. In the second O site, O(4) is bonded in a 2-coordinate geometry to one La(2), one Mn(2), and two equivalent Mn(1) atoms. In the third O site, O(5) is bonded in a distorted trigonal planar geometry to one Mn(2) and two equivalent Mn(1) atoms. In the fourth O site, O(6) is bonded in a 2-coordinate geometry to two equivalent La(2), one Mn(3), and one Si(2) atom. In the fifth O site, O(7) is bonded in a linear geometry to one Si(1) and one Si(2) atom. In the sixth O site, O(8) is bonded in a 3-coordinate geometry to one La(1), one La(2), and one Si(1) atom. In the seventh O site, O(1) is bonded in a 4-coordinate geometry to one La(1), one La(2), one Mn(1), and one Si(2) atom. In the eighth O site, O(2) is bonded in a distorted see-saw-like geometry to one La(1), one La(2), and two equivalent Mn(2) atoms.