La4Ti5(Si2O11)2 is Esseneite-like structured and 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 10-coordinate geometry to one O(1), one O(8), two equivalent O(2), two equivalent O(3), two equivalent O(5), and two equivalent O(6) atoms. In the second La site, La(2) is bonded in a 8-coordinate geometry to one O(1), one O(7), two equivalent O(3), two equivalent O(5), and two equivalent O(6) atoms. There are four inequivalent Ti sites. In the first Ti site, Ti(1) is bonded to two equivalent O(2) and four equivalent O(6) atoms to form TiO6 octahedra that share corners with two equivalent Si(2)O4 tetrahedra and corners with four equivalent Si(1)O4 tetrahedra. In the second Ti site, Ti(2) is bonded to two equivalent O(8) and four equivalent O(5) atoms to form a mixture of corner and edge-sharing TiO6 octahedra. The corner-sharing octahedral tilt angles are 47°. In the third Ti site, Ti(3) is bonded to two equivalent O(7) and four equivalent O(5) atoms to form a mixture of corner and edge-sharing TiO6 octahedra. The corner-sharing octahedral tilt angles are 46°. In the fourth Ti site, Ti(4) is bonded to two equivalent O(3), two equivalent O(7), and two equivalent O(8) atoms to form TiO6 octahedra that share corners with two equivalent Ti(2)O6 octahedra, corners with two equivalent Ti(3)O6 octahedra, corners with two equivalent Si(2)O4 tetrahedra, and edges with two equivalent Ti(4)O6 octahedra. The corner-sharing octahedral tilt angles range from 46-47°. There are two inequivalent Si sites. In the first Si site, Si(1) is bonded to one O(1), one O(4), and two equivalent O(6) atoms to form SiO4 tetrahedra that share corners with two equivalent Ti(1)O6 octahedra and  a cornercorner with one Si(2)O4 tetrahedra. The corner-sharing octahedral tilt angles are 44°. In the second Si site, Si(2) is bonded to one O(2), one O(4), and two equivalent O(3) atoms to form SiO4 tetrahedra that share  a cornercorner with one Ti(1)O6 octahedra, corners with two equivalent Ti(4)O6 octahedra, and  a cornercorner with one Si(1)O4 tetrahedra. The corner-sharing octahedral tilt angles range from 32-53°. There are eight inequivalent O sites. In the first O site, O(6) is bonded in a 4-coordinate geometry to one La(1), one La(2), one Ti(1), and one Si(1) atom. In the second O site, O(7) is bonded in a 3-coordinate geometry to one La(2), one Ti(3), and two equivalent Ti(4) atoms. In the third O site, O(8) is bonded in a 4-coordinate geometry to one La(1), one Ti(2), and two equivalent Ti(4) atoms. In the fourth O site, O(1) is bonded in a distorted single-bond geometry to one La(1), one La(2), and one Si(1) atom. In the fifth O site, O(2) is bonded in a bent 150 degrees geometry to two equivalent La(1), one Ti(1), and one Si(2) atom. In the sixth O site, O(3) is bonded in a 4-coordinate geometry to one La(1), one La(2), one Ti(4), and one Si(2) atom. In the seventh O site, O(4) is bonded in a linear geometry to one Si(1) and one Si(2) atom. In the eighth O site, O(5) is bonded in a distorted see-saw-like geometry to one La(1), one La(2), one Ti(2), and one Ti(3) atom.
La4Ti5(Si2O11)2 is Esseneite-like structured and 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 10-coordinate geometry to one O(1), one O(8), two equivalent O(2), two equivalent O(3), two equivalent O(5), and two equivalent O(6) atoms. The La(1)-O(1) bond length is 2.56 Å. The La(1)-O(8) bond length is 2.60 Å. Both La(1)-O(2) bond lengths are 3.07 Å. Both La(1)-O(3) bond lengths are 2.61 Å. Both La(1)-O(5) bond lengths are 2.45 Å. Both La(1)-O(6) bond lengths are 2.73 Å. In the second La site, La(2) is bonded in a 8-coordinate geometry to one O(1), one O(7), two equivalent O(3), two equivalent O(5), and two equivalent O(6) atoms. The La(2)-O(1) bond length is 2.58 Å. The La(2)-O(7) bond length is 2.72 Å. Both La(2)-O(3) bond lengths are 2.62 Å. Both La(2)-O(5) bond lengths are 2.43 Å. Both La(2)-O(6) bond lengths are 2.63 Å. There are four inequivalent Ti sites. In the first Ti site, Ti(1) is bonded to two equivalent O(2) and four equivalent O(6) atoms to form TiO6 octahedra that share corners with two equivalent Si(2)O4 tetrahedra and corners with four equivalent Si(1)O4 tetrahedra. Both Ti(1)-O(2) bond lengths are 1.96 Å. All Ti(1)-O(6) bond lengths are 2.13 Å. In the second Ti site, Ti(2) is bonded to two equivalent O(8) and four equivalent O(5) atoms to form a mixture of corner and edge-sharing TiO6 octahedra. The corner-sharing octahedral tilt angles are 47°. Both Ti(2)-O(8) bond lengths are 2.04 Å. All Ti(2)-O(5) bond lengths are 2.04 Å. In the third Ti site, Ti(3) is bonded to two equivalent O(7) and four equivalent O(5) atoms to form a mixture of corner and edge-sharing TiO6 octahedra. The corner-sharing octahedral tilt angles are 46°. Both Ti(3)-O(7) bond lengths are 2.03 Å. All Ti(3)-O(5) bond lengths are 2.04 Å. In the fourth Ti site, Ti(4) is bonded to two equivalent O(3), two equivalent O(7), and two equivalent O(8) atoms to form TiO6 octahedra that share corners with two equivalent Ti(2)O6 octahedra, corners with two equivalent Ti(3)O6 octahedra, corners with two equivalent Si(2)O4 tetrahedra, and edges with two equivalent Ti(4)O6 octahedra. The corner-sharing octahedral tilt angles range from 46-47°. Both Ti(4)-O(3) bond lengths are 2.05 Å. Both Ti(4)-O(7) bond lengths are 2.02 Å. Both Ti(4)-O(8) bond lengths are 2.03 Å. There are two inequivalent Si sites. In the first Si site, Si(1) is bonded to one O(1), one O(4), and two equivalent O(6) atoms to form SiO4 tetrahedra that share corners with two equivalent Ti(1)O6 octahedra and  a cornercorner with one Si(2)O4 tetrahedra. The corner-sharing octahedral tilt angles are 44°. The Si(1)-O(1) bond length is 1.60 Å. The Si(1)-O(4) bond length is 1.65 Å. Both Si(1)-O(6) bond lengths are 1.66 Å. In the second Si site, Si(2) is bonded to one O(2), one O(4), and two equivalent O(3) atoms to form SiO4 tetrahedra that share  a cornercorner with one Ti(1)O6 octahedra, corners with two equivalent Ti(4)O6 octahedra, and  a cornercorner with one Si(1)O4 tetrahedra. The corner-sharing octahedral tilt angles range from 32-53°. The Si(2)-O(2) bond length is 1.61 Å. The Si(2)-O(4) bond length is 1.62 Å. Both Si(2)-O(3) bond lengths are 1.64 Å. There are eight inequivalent O sites. In the first O site, O(6) is bonded in a 4-coordinate geometry to one La(1), one La(2), one Ti(1), and one Si(1) atom. In the second O site, O(7) is bonded in a 3-coordinate geometry to one La(2), one Ti(3), and two equivalent Ti(4) atoms. In the third O site, O(8) is bonded in a 4-coordinate geometry to one La(1), one Ti(2), and two equivalent Ti(4) atoms. In the fourth O site, O(1) is bonded in a distorted single-bond geometry to one La(1), one La(2), and one Si(1) atom. In the fifth O site, O(2) is bonded in a bent 150 degrees geometry to two equivalent La(1), one Ti(1), and one Si(2) atom. In the sixth O site, O(3) is bonded in a 4-coordinate geometry to one La(1), one La(2), one Ti(4), and one Si(2) atom. In the seventh O site, O(4) is bonded in a linear geometry to one Si(1) and one Si(2) atom. In the eighth O site, O(5) is bonded in a distorted see-saw-like geometry to one La(1), one La(2), one Ti(2), and one Ti(3) atom.