Ba3La3Ti4NbO18 crystallizes in the trigonal R3m space group. There are three inequivalent Ba sites. In the first Ba site, Ba(1) is bonded to three equivalent O(4), three equivalent O(6), and six equivalent O(3) atoms to form BaO12 cuboctahedra that share corners with three equivalent Ba(3)O12 cuboctahedra, corners with six equivalent Ba(1)O12 cuboctahedra, faces with three equivalent La(3)O12 cuboctahedra,  a faceface with one Ti(1)O6 octahedra,  a faceface with one Ti(2)O6 octahedra, faces with three equivalent Ti(3)O6 octahedra, and faces with three equivalent Ti(4)O6 octahedra. In the second Ba site, Ba(2) is bonded to three equivalent O(1), three equivalent O(2), and six equivalent O(5) atoms to form distorted BaO12 cuboctahedra that share corners with three equivalent La(3)O12 cuboctahedra, corners with six equivalent Ba(2)O12 cuboctahedra, corners with three equivalent Ti(1)O6 octahedra, faces with three equivalent Ba(3)O12 cuboctahedra,  a faceface with one Ti(2)O6 octahedra, and faces with three equivalent Nb(1)O6 octahedra. The corner-sharing octahedral tilt angles are 28°. In the third Ba site, Ba(3) is bonded to three equivalent O(4), three equivalent O(5), and six equivalent O(1) atoms to form BaO12 cuboctahedra that share corners with three equivalent Ba(1)O12 cuboctahedra, corners with six equivalent Ba(3)O12 cuboctahedra, faces with three equivalent Ba(2)O12 cuboctahedra, faces with three equivalent La(3)O12 cuboctahedra,  a faceface with one Ti(3)O6 octahedra, faces with three equivalent Ti(2)O6 octahedra, and faces with three equivalent Nb(1)O6 octahedra. There are three inequivalent La sites. In the first La site, La(1) is bonded in a 12-coordinate geometry to three equivalent O(2), three equivalent O(3), and six equivalent O(6) atoms. In the second La site, La(2) is bonded in a 12-coordinate geometry to three equivalent O(5), three equivalent O(6), and six equivalent O(2) atoms. In the third La site, La(3) is bonded to three equivalent O(1), three equivalent O(3), and six equivalent O(4) atoms to form LaO12 cuboctahedra that share corners with three equivalent Ba(2)O12 cuboctahedra, corners with six equivalent La(3)O12 cuboctahedra, faces with three equivalent Ba(1)O12 cuboctahedra, faces with three equivalent Ba(3)O12 cuboctahedra,  a faceface with one Ti(4)O6 octahedra,  a faceface with one Nb(1)O6 octahedra, faces with three equivalent Ti(2)O6 octahedra, and faces with three equivalent Ti(3)O6 octahedra. There are four inequivalent Ti sites. In the first Ti site, Ti(1) is bonded to three equivalent O(2) and three equivalent O(6) atoms to form TiO6 octahedra that share corners with three equivalent Ba(2)O12 cuboctahedra, corners with three equivalent Ti(4)O6 octahedra, and  a faceface with one Ba(1)O12 cuboctahedra. The corner-sharing octahedral tilt angles are 7°. In the second Ti site, Ti(2) is bonded to three equivalent O(1) and three equivalent O(4) atoms to form TiO6 octahedra that share corners with three equivalent Ti(3)O6 octahedra, corners with three equivalent Nb(1)O6 octahedra,  a faceface with one Ba(1)O12 cuboctahedra,  a faceface with one Ba(2)O12 cuboctahedra, faces with three equivalent Ba(3)O12 cuboctahedra, and faces with three equivalent La(3)O12 cuboctahedra. The corner-sharing octahedral tilt angles range from 1-9°. In the third Ti site, Ti(3) is bonded to three equivalent O(3) and three equivalent O(4) atoms to form TiO6 octahedra that share corners with three equivalent Ti(2)O6 octahedra, corners with three equivalent Ti(4)O6 octahedra,  a faceface with one Ba(3)O12 cuboctahedra, faces with three equivalent Ba(1)O12 cuboctahedra, and faces with three equivalent La(3)O12 cuboctahedra. The corner-sharing octahedral tilt angles range from 1-8°. In the fourth Ti site, Ti(4) is bonded to three equivalent O(3) and three equivalent O(6) 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(3)O12 cuboctahedra, and faces with three equivalent Ba(1)O12 cuboctahedra. The corner-sharing octahedral tilt angles range from 7-8°. Nb(1) is bonded to three equivalent O(1) and three equivalent O(5) atoms to form NbO6 octahedra that share corners with three equivalent Ti(2)O6 octahedra,  a faceface with one La(3)O12 cuboctahedra, faces with three equivalent Ba(2)O12 cuboctahedra, and faces with three equivalent Ba(3)O12 cuboctahedra. The corner-sharing octahedral tilt angles are 9°. There are six inequivalent O sites. In the first O site, O(1) is bonded in a 2-coordinate geometry to one Ba(2), two equivalent Ba(3), one La(3), one Ti(2), and one Nb(1) atom. In the second O site, O(2) is bonded in a 5-coordinate geometry to one Ba(2), one La(1), two equivalent La(2), and one Ti(1) atom. In the third O site, O(3) is bonded in a distorted linear geometry to two equivalent Ba(1), one La(1), one La(3), one Ti(3), and one Ti(4) atom. In the fourth O site, O(4) is bonded in a distorted linear geometry to one Ba(1), one Ba(3), two equivalent La(3), one Ti(2), and one Ti(3) atom. In the fifth O site, O(5) is bonded in a 5-coordinate geometry to one Ba(3), two equivalent Ba(2), one La(2), and one Nb(1) atom. In the sixth O site, O(6) is bonded in a 2-coordinate geometry to one Ba(1), one La(2), two equivalent La(1), one Ti(1), and one Ti(4) atom.
Ba3La3Ti4NbO18 crystallizes in the trigonal R3m space group. There are three inequivalent Ba sites. In the first Ba site, Ba(1) is bonded to three equivalent O(4), three equivalent O(6), and six equivalent O(3) atoms to form BaO12 cuboctahedra that share corners with three equivalent Ba(3)O12 cuboctahedra, corners with six equivalent Ba(1)O12 cuboctahedra, faces with three equivalent La(3)O12 cuboctahedra,  a faceface with one Ti(1)O6 octahedra,  a faceface with one Ti(2)O6 octahedra, faces with three equivalent Ti(3)O6 octahedra, and faces with three equivalent Ti(4)O6 octahedra. All Ba(1)-O(4) bond lengths are 2.83 Å. All Ba(1)-O(6) bond lengths are 2.77 Å. All Ba(1)-O(3) bond lengths are 2.84 Å. In the second Ba site, Ba(2) is bonded to three equivalent O(1), three equivalent O(2), and six equivalent O(5) atoms to form distorted BaO12 cuboctahedra that share corners with three equivalent La(3)O12 cuboctahedra, corners with six equivalent Ba(2)O12 cuboctahedra, corners with three equivalent Ti(1)O6 octahedra, faces with three equivalent Ba(3)O12 cuboctahedra,  a faceface with one Ti(2)O6 octahedra, and faces with three equivalent Nb(1)O6 octahedra. The corner-sharing octahedral tilt angles are 28°. All Ba(2)-O(1) bond lengths are 3.16 Å. All Ba(2)-O(2) bond lengths are 2.75 Å. All Ba(2)-O(5) bond lengths are 2.85 Å. In the third Ba site, Ba(3) is bonded to three equivalent O(4), three equivalent O(5), and six equivalent O(1) atoms to form BaO12 cuboctahedra that share corners with three equivalent Ba(1)O12 cuboctahedra, corners with six equivalent Ba(3)O12 cuboctahedra, faces with three equivalent Ba(2)O12 cuboctahedra, faces with three equivalent La(3)O12 cuboctahedra,  a faceface with one Ti(3)O6 octahedra, faces with three equivalent Ti(2)O6 octahedra, and faces with three equivalent Nb(1)O6 octahedra. All Ba(3)-O(4) bond lengths are 2.87 Å. All Ba(3)-O(5) bond lengths are 2.80 Å. All Ba(3)-O(1) bond lengths are 2.85 Å. There are three inequivalent La sites. In the first La site, La(1) is bonded in a 12-coordinate geometry to three equivalent O(2), three equivalent O(3), and six equivalent O(6) atoms. All La(1)-O(2) bond lengths are 2.42 Å. All La(1)-O(3) bond lengths are 3.13 Å. All La(1)-O(6) bond lengths are 2.86 Å. In the second La site, La(2) is bonded in a 12-coordinate geometry to three equivalent O(5), three equivalent O(6), and six equivalent O(2) atoms. All La(2)-O(5) bond lengths are 2.50 Å. All La(2)-O(6) bond lengths are 3.18 Å. All La(2)-O(2) bond lengths are 2.90 Å. In the third La site, La(3) is bonded to three equivalent O(1), three equivalent O(3), and six equivalent O(4) atoms to form LaO12 cuboctahedra that share corners with three equivalent Ba(2)O12 cuboctahedra, corners with six equivalent La(3)O12 cuboctahedra, faces with three equivalent Ba(1)O12 cuboctahedra, faces with three equivalent Ba(3)O12 cuboctahedra,  a faceface with one Ti(4)O6 octahedra,  a faceface with one Nb(1)O6 octahedra, faces with three equivalent Ti(2)O6 octahedra, and faces with three equivalent Ti(3)O6 octahedra. All La(3)-O(1) bond lengths are 2.73 Å. All La(3)-O(3) bond lengths are 2.75 Å. All La(3)-O(4) bond lengths are 2.84 Å. There are four inequivalent Ti sites. In the first Ti site, Ti(1) is bonded to three equivalent O(2) and three equivalent O(6) atoms to form TiO6 octahedra that share corners with three equivalent Ba(2)O12 cuboctahedra, corners with three equivalent Ti(4)O6 octahedra, and  a faceface with one Ba(1)O12 cuboctahedra. The corner-sharing octahedral tilt angles are 7°. All Ti(1)-O(2) bond lengths are 1.86 Å. All Ti(1)-O(6) bond lengths are 2.14 Å. In the second Ti site, Ti(2) is bonded to three equivalent O(1) and three equivalent O(4) atoms to form TiO6 octahedra that share corners with three equivalent Ti(3)O6 octahedra, corners with three equivalent Nb(1)O6 octahedra,  a faceface with one Ba(1)O12 cuboctahedra,  a faceface with one Ba(2)O12 cuboctahedra, faces with three equivalent Ba(3)O12 cuboctahedra, and faces with three equivalent La(3)O12 cuboctahedra. The corner-sharing octahedral tilt angles range from 1-9°. All Ti(2)-O(1) bond lengths are 1.97 Å. All Ti(2)-O(4) bond lengths are 2.00 Å. In the third Ti site, Ti(3) is bonded to three equivalent O(3) and three equivalent O(4) atoms to form TiO6 octahedra that share corners with three equivalent Ti(2)O6 octahedra, corners with three equivalent Ti(4)O6 octahedra,  a faceface with one Ba(3)O12 cuboctahedra, faces with three equivalent Ba(1)O12 cuboctahedra, and faces with three equivalent La(3)O12 cuboctahedra. The corner-sharing octahedral tilt angles range from 1-8°. All Ti(3)-O(3) bond lengths are 1.94 Å. All Ti(3)-O(4) bond lengths are 2.04 Å. In the fourth Ti site, Ti(4) is bonded to three equivalent O(3) and three equivalent O(6) 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(3)O12 cuboctahedra, and faces with three equivalent Ba(1)O12 cuboctahedra. The corner-sharing octahedral tilt angles range from 7-8°. All Ti(4)-O(3) bond lengths are 2.09 Å. All Ti(4)-O(6) bond lengths are 1.89 Å. Nb(1) is bonded to three equivalent O(1) and three equivalent O(5) atoms to form NbO6 octahedra that share corners with three equivalent Ti(2)O6 octahedra,  a faceface with one La(3)O12 cuboctahedra, faces with three equivalent Ba(2)O12 cuboctahedra, and faces with three equivalent Ba(3)O12 cuboctahedra. The corner-sharing octahedral tilt angles are 9°. All Nb(1)-O(1) bond lengths are 2.17 Å. All Nb(1)-O(5) bond lengths are 1.92 Å. There are six inequivalent O sites. In the first O site, O(1) is bonded in a 2-coordinate geometry to one Ba(2), two equivalent Ba(3), one La(3), one Ti(2), and one Nb(1) atom. In the second O site, O(2) is bonded in a 5-coordinate geometry to one Ba(2), one La(1), two equivalent La(2), and one Ti(1) atom. In the third O site, O(3) is bonded in a distorted linear geometry to two equivalent Ba(1), one La(1), one La(3), one Ti(3), and one Ti(4) atom. In the fourth O site, O(4) is bonded in a distorted linear geometry to one Ba(1), one Ba(3), two equivalent La(3), one Ti(2), and one Ti(3) atom. In the fifth O site, O(5) is bonded in a 5-coordinate geometry to one Ba(3), two equivalent Ba(2), one La(2), and one Nb(1) atom. In the sixth O site, O(6) is bonded in a 2-coordinate geometry to one Ba(1), one La(2), two equivalent La(1), one Ti(1), and one Ti(4) atom.