La2Ti3O9 crystallizes in the monoclinic C2/m space group. There are three inequivalent La sites. In the first La site, La(1) is bonded to two equivalent O(2), two equivalent O(6), four equivalent O(4), and four equivalent O(7) atoms to form LaO12 cuboctahedra that share corners with two equivalent La(1)O12 cuboctahedra, corners with two equivalent La(2)O12 cuboctahedra, corners with four equivalent La(3)O12 cuboctahedra, faces with four equivalent La(2)O12 cuboctahedra, faces with two equivalent Ti(1)O6 octahedra, faces with two equivalent Ti(2)O6 octahedra, and faces with four equivalent Ti(3)O6 octahedra. In the second La site, La(2) is bonded to one O(6), two equivalent O(4), two equivalent O(7), three equivalent O(2), and four equivalent O(5) atoms to form LaO12 cuboctahedra that share  a cornercorner with one La(1)O12 cuboctahedra, corners with two equivalent La(3)O12 cuboctahedra, corners with three equivalent La(2)O12 cuboctahedra,  a faceface with one La(3)O12 cuboctahedra, faces with two equivalent La(1)O12 cuboctahedra, faces with two equivalent La(2)O12 cuboctahedra, faces with two equivalent Ti(3)O6 octahedra, faces with three equivalent Ti(1)O6 octahedra, and faces with three equivalent Ti(2)O6 octahedra. In the third La site, La(3) is bonded to two equivalent O(1), two equivalent O(3), four equivalent O(4), and four equivalent O(5) atoms to form LaO12 cuboctahedra that share corners with two equivalent La(3)O12 cuboctahedra, corners with four equivalent La(1)O12 cuboctahedra, corners with four equivalent La(2)O12 cuboctahedra, faces with two equivalent La(2)O12 cuboctahedra, faces with two equivalent Ti(2)O6 octahedra, faces with two equivalent Ti(3)O6 octahedra, and faces with four equivalent Ti(1)O6 octahedra. There are three inequivalent Ti sites. In the first Ti site, Ti(1) is bonded to one O(1), one O(2), two equivalent O(4), and two equivalent O(5) atoms to form TiO6 octahedra that share  a cornercorner with one Ti(1)O6 octahedra, corners with two equivalent Ti(3)O6 octahedra, corners with three equivalent Ti(2)O6 octahedra,  a faceface with one La(1)O12 cuboctahedra, faces with two equivalent La(3)O12 cuboctahedra, and faces with three equivalent La(2)O12 cuboctahedra. The corner-sharing octahedral tilt angles range from 0-12°. In the second Ti site, Ti(2) is bonded to one O(2), one O(3), two equivalent O(5), and two equivalent O(7) atoms to form TiO6 octahedra that share corners with three equivalent Ti(1)O6 octahedra, corners with three equivalent Ti(3)O6 octahedra,  a faceface with one La(1)O12 cuboctahedra,  a faceface with one La(3)O12 cuboctahedra, and faces with three equivalent La(2)O12 cuboctahedra. The corner-sharing octahedral tilt angles range from 3-18°. In the third Ti site, Ti(3) is bonded to one O(3), one O(6), two equivalent O(4), and two equivalent O(7) atoms to form TiO6 octahedra that share  a cornercorner with one Ti(3)O6 octahedra, corners with two equivalent Ti(1)O6 octahedra, corners with three equivalent Ti(2)O6 octahedra,  a faceface with one La(3)O12 cuboctahedra, faces with two equivalent La(1)O12 cuboctahedra, and faces with two equivalent La(2)O12 cuboctahedra. The corner-sharing octahedral tilt angles range from 0-18°. There are seven inequivalent O sites. In the first O site, O(1) is bonded in a distorted linear geometry to two equivalent La(3) and two equivalent Ti(1) atoms. In the second O site, O(2) is bonded to one La(1), three equivalent La(2), one Ti(1), and one Ti(2) atom to form distorted OLa4Ti2 octahedra that share corners with three equivalent O(2)La4Ti2 octahedra, corners with four equivalent O(5)La3Ti2 square pyramids, corners with six equivalent O(4)La3Ti2 square pyramids, edges with two equivalent O(2)La4Ti2 octahedra, faces with two equivalent O(4)La3Ti2 square pyramids, and faces with four equivalent O(5)La3Ti2 square pyramids. The corner-sharing octahedral tilt angles range from 0-1°. In the third O site, O(3) is bonded in a distorted T-shaped geometry to one La(3), one Ti(2), and one Ti(3) atom. In the fourth O site, O(4) is bonded to one La(1), one La(2), one La(3), one Ti(1), and one Ti(3) atom to form distorted OLa3Ti2 square pyramids that share corners with three equivalent O(2)La4Ti2 octahedra, corners with four equivalent O(4)La3Ti2 square pyramids, corners with five equivalent O(5)La3Ti2 square pyramids,  an edgeedge with one O(4)La3Ti2 square pyramid,  an edgeedge with one O(5)La3Ti2 square pyramid,  a faceface with one O(2)La4Ti2 octahedra,  a faceface with one O(4)La3Ti2 square pyramid, and  a faceface with one O(5)La3Ti2 square pyramid. The corner-sharing octahedral tilt angles range from 58-60°. In the fifth O site, O(5) is bonded to one La(3), two equivalent La(2), one Ti(1), and one Ti(2) atom to form distorted OLa3Ti2 square pyramids that share corners with two equivalent O(2)La4Ti2 octahedra, corners with four equivalent O(5)La3Ti2 square pyramids, corners with five equivalent O(4)La3Ti2 square pyramids,  an edgeedge with one O(4)La3Ti2 square pyramid, edges with two equivalent O(5)La3Ti2 square pyramids, faces with two equivalent O(2)La4Ti2 octahedra,  a faceface with one O(4)La3Ti2 square pyramid, and  a faceface with one O(5)La3Ti2 square pyramid. The corner-sharing octahedral tilt angles range from 59-61°. In the sixth O site, O(6) is bonded in a distorted linear geometry to two equivalent La(1), two equivalent La(2), and two equivalent Ti(3) atoms. In the seventh O site, O(7) is bonded in a distorted rectangular see-saw-like geometry to one La(1), one La(2), one Ti(2), and one Ti(3) atom.
La2Ti3O9 crystallizes in the monoclinic C2/m space group. There are three inequivalent La sites. In the first La site, La(1) is bonded to two equivalent O(2), two equivalent O(6), four equivalent O(4), and four equivalent O(7) atoms to form LaO12 cuboctahedra that share corners with two equivalent La(1)O12 cuboctahedra, corners with two equivalent La(2)O12 cuboctahedra, corners with four equivalent La(3)O12 cuboctahedra, faces with four equivalent La(2)O12 cuboctahedra, faces with two equivalent Ti(1)O6 octahedra, faces with two equivalent Ti(2)O6 octahedra, and faces with four equivalent Ti(3)O6 octahedra. Both La(1)-O(2) bond lengths are 2.78 Å. Both La(1)-O(6) bond lengths are 2.75 Å. All La(1)-O(4) bond lengths are 2.75 Å. All La(1)-O(7) bond lengths are 2.63 Å. In the second La site, La(2) is bonded to one O(6), two equivalent O(4), two equivalent O(7), three equivalent O(2), and four equivalent O(5) atoms to form LaO12 cuboctahedra that share  a cornercorner with one La(1)O12 cuboctahedra, corners with two equivalent La(3)O12 cuboctahedra, corners with three equivalent La(2)O12 cuboctahedra,  a faceface with one La(3)O12 cuboctahedra, faces with two equivalent La(1)O12 cuboctahedra, faces with two equivalent La(2)O12 cuboctahedra, faces with two equivalent Ti(3)O6 octahedra, faces with three equivalent Ti(1)O6 octahedra, and faces with three equivalent Ti(2)O6 octahedra. The La(2)-O(6) bond length is 2.76 Å. Both La(2)-O(4) bond lengths are 2.63 Å. Both La(2)-O(7) bond lengths are 2.63 Å. There is one shorter (2.73 Å) and two longer (2.75 Å) La(2)-O(2) bond lengths. There are two shorter (2.64 Å) and two longer (2.76 Å) La(2)-O(5) bond lengths. In the third La site, La(3) is bonded to two equivalent O(1), two equivalent O(3), four equivalent O(4), and four equivalent O(5) atoms to form LaO12 cuboctahedra that share corners with two equivalent La(3)O12 cuboctahedra, corners with four equivalent La(1)O12 cuboctahedra, corners with four equivalent La(2)O12 cuboctahedra, faces with two equivalent La(2)O12 cuboctahedra, faces with two equivalent Ti(2)O6 octahedra, faces with two equivalent Ti(3)O6 octahedra, and faces with four equivalent Ti(1)O6 octahedra. Both La(3)-O(1) bond lengths are 2.75 Å. Both La(3)-O(3) bond lengths are 2.55 Å. All La(3)-O(4) bond lengths are 2.79 Å. All La(3)-O(5) bond lengths are 2.78 Å. There are three inequivalent Ti sites. In the first Ti site, Ti(1) is bonded to one O(1), one O(2), two equivalent O(4), and two equivalent O(5) atoms to form TiO6 octahedra that share  a cornercorner with one Ti(1)O6 octahedra, corners with two equivalent Ti(3)O6 octahedra, corners with three equivalent Ti(2)O6 octahedra,  a faceface with one La(1)O12 cuboctahedra, faces with two equivalent La(3)O12 cuboctahedra, and faces with three equivalent La(2)O12 cuboctahedra. The corner-sharing octahedral tilt angles range from 0-12°. The Ti(1)-O(1) bond length is 1.93 Å. The Ti(1)-O(2) bond length is 1.99 Å. Both Ti(1)-O(4) bond lengths are 1.96 Å. Both Ti(1)-O(5) bond lengths are 1.96 Å. In the second Ti site, Ti(2) is bonded to one O(2), one O(3), two equivalent O(5), and two equivalent O(7) atoms to form TiO6 octahedra that share corners with three equivalent Ti(1)O6 octahedra, corners with three equivalent Ti(3)O6 octahedra,  a faceface with one La(1)O12 cuboctahedra,  a faceface with one La(3)O12 cuboctahedra, and faces with three equivalent La(2)O12 cuboctahedra. The corner-sharing octahedral tilt angles range from 3-18°. The Ti(2)-O(2) bond length is 2.10 Å. The Ti(2)-O(3) bond length is 1.87 Å. Both Ti(2)-O(5) bond lengths are 2.00 Å. Both Ti(2)-O(7) bond lengths are 1.93 Å. In the third Ti site, Ti(3) is bonded to one O(3), one O(6), two equivalent O(4), and two equivalent O(7) atoms to form TiO6 octahedra that share  a cornercorner with one Ti(3)O6 octahedra, corners with two equivalent Ti(1)O6 octahedra, corners with three equivalent Ti(2)O6 octahedra,  a faceface with one La(3)O12 cuboctahedra, faces with two equivalent La(1)O12 cuboctahedra, and faces with two equivalent La(2)O12 cuboctahedra. The corner-sharing octahedral tilt angles range from 0-18°. The Ti(3)-O(3) bond length is 1.89 Å. The Ti(3)-O(6) bond length is 2.05 Å. Both Ti(3)-O(4) bond lengths are 2.00 Å. Both Ti(3)-O(7) bond lengths are 1.93 Å. There are seven inequivalent O sites. In the first O site, O(1) is bonded in a distorted linear geometry to two equivalent La(3) and two equivalent Ti(1) atoms. In the second O site, O(2) is bonded to one La(1), three equivalent La(2), one Ti(1), and one Ti(2) atom to form distorted OLa4Ti2 octahedra that share corners with three equivalent O(2)La4Ti2 octahedra, corners with four equivalent O(5)La3Ti2 square pyramids, corners with six equivalent O(4)La3Ti2 square pyramids, edges with two equivalent O(2)La4Ti2 octahedra, faces with two equivalent O(4)La3Ti2 square pyramids, and faces with four equivalent O(5)La3Ti2 square pyramids. The corner-sharing octahedral tilt angles range from 0-1°. In the third O site, O(3) is bonded in a distorted T-shaped geometry to one La(3), one Ti(2), and one Ti(3) atom. In the fourth O site, O(4) is bonded to one La(1), one La(2), one La(3), one Ti(1), and one Ti(3) atom to form distorted OLa3Ti2 square pyramids that share corners with three equivalent O(2)La4Ti2 octahedra, corners with four equivalent O(4)La3Ti2 square pyramids, corners with five equivalent O(5)La3Ti2 square pyramids,  an edgeedge with one O(4)La3Ti2 square pyramid,  an edgeedge with one O(5)La3Ti2 square pyramid,  a faceface with one O(2)La4Ti2 octahedra,  a faceface with one O(4)La3Ti2 square pyramid, and  a faceface with one O(5)La3Ti2 square pyramid. The corner-sharing octahedral tilt angles range from 58-60°. In the fifth O site, O(5) is bonded to one La(3), two equivalent La(2), one Ti(1), and one Ti(2) atom to form distorted OLa3Ti2 square pyramids that share corners with two equivalent O(2)La4Ti2 octahedra, corners with four equivalent O(5)La3Ti2 square pyramids, corners with five equivalent O(4)La3Ti2 square pyramids,  an edgeedge with one O(4)La3Ti2 square pyramid, edges with two equivalent O(5)La3Ti2 square pyramids, faces with two equivalent O(2)La4Ti2 octahedra,  a faceface with one O(4)La3Ti2 square pyramid, and  a faceface with one O(5)La3Ti2 square pyramid. The corner-sharing octahedral tilt angles range from 59-61°. In the sixth O site, O(6) is bonded in a distorted linear geometry to two equivalent La(1), two equivalent La(2), and two equivalent Ti(3) atoms. In the seventh O site, O(7) is bonded in a distorted rectangular see-saw-like geometry to one La(1), one La(2), one Ti(2), and one Ti(3) atom.