Ba4Ti4O9 crystallizes in the monoclinic C2/m space group. There are three inequivalent Ba sites. In the first Ba site, Ba(1) is bonded in a distorted q6 geometry to one O(10), one O(12), one O(2), one O(4), one O(7), one O(9), and three equivalent O(1) atoms. In the second Ba site, Ba(2) is bonded in a distorted q6 geometry to one O(1), one O(10), one O(3), one O(4), one O(5), one O(6), one O(7), and two equivalent O(2) atoms. In the third Ba site, Ba(3) is bonded in a distorted q6 geometry to one O(11), one O(2), one O(5), one O(6), two equivalent O(8), and three equivalent O(3) atoms. There are six inequivalent Ti sites. In the first Ti site, Ti(1) is bonded to one O(10), one O(4), one O(5), and two equivalent O(2) atoms to form corner-sharing TiO5 square pyramids. In the second Ti site, Ti(2) is bonded in a rectangular see-saw-like geometry to one O(5), one O(8), and two equivalent O(3) atoms. In the third Ti site, Ti(3) is bonded to one O(11), one O(6), one O(8), and two equivalent O(3) atoms to form corner-sharing TiO5 square pyramids. In the fourth Ti site, Ti(4) is bonded in a square co-planar geometry to one O(6), one O(7), and two equivalent O(2) atoms. In the fifth Ti site, Ti(5) is bonded to one O(10), one O(7), one O(9), and two equivalent O(1) atoms to form corner-sharing TiO5 square pyramids. In the sixth Ti site, Ti(6) is bonded in a rectangular see-saw-like geometry to one O(12), one O(4), and two equivalent O(1) atoms. There are twelve inequivalent O sites. In the first O site, O(1) is bonded to one Ba(2), three equivalent Ba(1), one Ti(5), and one Ti(6) atom to form a mixture of distorted edge, corner, and face-sharing OBa4Ti2 octahedra. The corner-sharing octahedral tilt angles range from 1-60°. In the second O site, O(2) is bonded to one Ba(1), one Ba(3), two equivalent Ba(2), one Ti(1), and one Ti(4) atom to form a mixture of distorted edge, corner, and face-sharing OBa4Ti2 octahedra. The corner-sharing octahedral tilt angles range from 1-59°. In the third O site, O(3) is bonded to one Ba(2), three equivalent Ba(3), one Ti(2), and one Ti(3) atom to form a mixture of distorted edge, corner, and face-sharing OBa4Ti2 octahedra. The corner-sharing octahedral tilt angles range from 1-60°. In the fourth O site, O(4) is bonded to two equivalent Ba(1), two equivalent Ba(2), one Ti(1), and one Ti(6) atom to form a mixture of distorted edge, corner, and face-sharing OBa4Ti2 octahedra. The corner-sharing octahedral tilt angles range from 1-59°. In the fifth O site, O(5) is bonded to two equivalent Ba(2), two equivalent Ba(3), one Ti(1), and one Ti(2) atom to form a mixture of distorted edge, corner, and face-sharing OBa4Ti2 octahedra. The corner-sharing octahedral tilt angles range from 1-59°. In the sixth O site, O(6) is bonded to two equivalent Ba(2), two equivalent Ba(3), one Ti(3), and one Ti(4) atom to form a mixture of distorted edge, corner, and face-sharing OBa4Ti2 octahedra. The corner-sharing octahedral tilt angles range from 1-59°. In the seventh O site, O(7) is bonded to two equivalent Ba(1), two equivalent Ba(2), one Ti(4), and one Ti(5) atom to form a mixture of distorted edge, corner, and face-sharing OBa4Ti2 octahedra. The corner-sharing octahedral tilt angles range from 1-60°. In the eighth O site, O(8) is bonded to four equivalent Ba(3), one Ti(2), and one Ti(3) atom to form a mixture of distorted edge, corner, and face-sharing OBa4Ti2 octahedra. The corner-sharing octahedral tilt angles range from 1-59°. In the ninth O site, O(9) is bonded to four equivalent Ba(1) and two equivalent Ti(5) atoms to form a mixture of distorted edge, corner, and face-sharing OBa4Ti2 octahedra. The corner-sharing octahedral tilt angles range from 1-59°. In the tenth O site, O(10) is bonded in a distorted linear geometry to two equivalent Ba(1), two equivalent Ba(2), one Ti(1), and one Ti(5) atom. In the eleventh O site, O(11) is bonded in a distorted linear geometry to four equivalent Ba(3) and two equivalent Ti(3) atoms. In the twelfth O site, O(12) is bonded to four equivalent Ba(1) and two equivalent Ti(6) atoms to form a mixture of distorted edge, corner, and face-sharing OBa4Ti2 octahedra. The corner-sharing octahedral tilt angles range from 1-59°.
Ba4Ti4O9 crystallizes in the monoclinic C2/m space group. There are three inequivalent Ba sites. In the first Ba site, Ba(1) is bonded in a distorted q6 geometry to one O(10), one O(12), one O(2), one O(4), one O(7), one O(9), and three equivalent O(1) atoms. The Ba(1)-O(10) bond length is 2.87 Å. The Ba(1)-O(12) bond length is 2.87 Å. The Ba(1)-O(2) bond length is 2.94 Å. The Ba(1)-O(4) bond length is 2.92 Å. The Ba(1)-O(7) bond length is 2.84 Å. The Ba(1)-O(9) bond length is 2.89 Å. There are two shorter (2.84 Å) and one longer (2.92 Å) Ba(1)-O(1) bond length. In the second Ba site, Ba(2) is bonded in a distorted q6 geometry to one O(1), one O(10), one O(3), one O(4), one O(5), one O(6), one O(7), and two equivalent O(2) atoms. The Ba(2)-O(1) bond length is 2.93 Å. The Ba(2)-O(10) bond length is 2.86 Å. The Ba(2)-O(3) bond length is 2.84 Å. The Ba(2)-O(4) bond length is 2.83 Å. The Ba(2)-O(5) bond length is 2.93 Å. The Ba(2)-O(6) bond length is 2.83 Å. The Ba(2)-O(7) bond length is 2.92 Å. There is one shorter (2.83 Å) and one longer (2.93 Å) Ba(2)-O(2) bond length. In the third Ba site, Ba(3) is bonded in a distorted q6 geometry to one O(11), one O(2), one O(5), one O(6), two equivalent O(8), and three equivalent O(3) atoms. The Ba(3)-O(11) bond length is 2.87 Å. The Ba(3)-O(2) bond length is 2.83 Å. The Ba(3)-O(5) bond length is 2.83 Å. The Ba(3)-O(6) bond length is 2.93 Å. There is one shorter (2.83 Å) and one longer (2.92 Å) Ba(3)-O(8) bond length. There is one shorter (2.83 Å) and two longer (2.93 Å) Ba(3)-O(3) bond lengths. There are six inequivalent Ti sites. In the first Ti site, Ti(1) is bonded to one O(10), one O(4), one O(5), and two equivalent O(2) atoms to form corner-sharing TiO5 square pyramids. The Ti(1)-O(10) bond length is 1.93 Å. The Ti(1)-O(4) bond length is 2.05 Å. The Ti(1)-O(5) bond length is 2.01 Å. Both Ti(1)-O(2) bond lengths are 2.02 Å. In the second Ti site, Ti(2) is bonded in a rectangular see-saw-like geometry to one O(5), one O(8), and two equivalent O(3) atoms. The Ti(2)-O(5) bond length is 2.01 Å. The Ti(2)-O(8) bond length is 1.99 Å. Both Ti(2)-O(3) bond lengths are 1.99 Å. In the third Ti site, Ti(3) is bonded to one O(11), one O(6), one O(8), and two equivalent O(3) atoms to form corner-sharing TiO5 square pyramids. The Ti(3)-O(11) bond length is 1.93 Å. The Ti(3)-O(6) bond length is 2.02 Å. The Ti(3)-O(8) bond length is 2.03 Å. Both Ti(3)-O(3) bond lengths are 2.03 Å. In the fourth Ti site, Ti(4) is bonded in a square co-planar geometry to one O(6), one O(7), and two equivalent O(2) atoms. The Ti(4)-O(6) bond length is 2.01 Å. The Ti(4)-O(7) bond length is 1.98 Å. Both Ti(4)-O(2) bond lengths are 2.00 Å. In the fifth Ti site, Ti(5) is bonded to one O(10), one O(7), one O(9), and two equivalent O(1) atoms to form corner-sharing TiO5 square pyramids. The Ti(5)-O(10) bond length is 1.94 Å. The Ti(5)-O(7) bond length is 2.05 Å. The Ti(5)-O(9) bond length is 2.00 Å. Both Ti(5)-O(1) bond lengths are 2.03 Å. In the sixth Ti site, Ti(6) is bonded in a rectangular see-saw-like geometry to one O(12), one O(4), and two equivalent O(1) atoms. The Ti(6)-O(12) bond length is 2.02 Å. The Ti(6)-O(4) bond length is 1.99 Å. Both Ti(6)-O(1) bond lengths are 1.99 Å. There are twelve inequivalent O sites. In the first O site, O(1) is bonded to one Ba(2), three equivalent Ba(1), one Ti(5), and one Ti(6) atom to form a mixture of distorted edge, corner, and face-sharing OBa4Ti2 octahedra. The corner-sharing octahedral tilt angles range from 1-60°. In the second O site, O(2) is bonded to one Ba(1), one Ba(3), two equivalent Ba(2), one Ti(1), and one Ti(4) atom to form a mixture of distorted edge, corner, and face-sharing OBa4Ti2 octahedra. The corner-sharing octahedral tilt angles range from 1-59°. In the third O site, O(3) is bonded to one Ba(2), three equivalent Ba(3), one Ti(2), and one Ti(3) atom to form a mixture of distorted edge, corner, and face-sharing OBa4Ti2 octahedra. The corner-sharing octahedral tilt angles range from 1-60°. In the fourth O site, O(4) is bonded to two equivalent Ba(1), two equivalent Ba(2), one Ti(1), and one Ti(6) atom to form a mixture of distorted edge, corner, and face-sharing OBa4Ti2 octahedra. The corner-sharing octahedral tilt angles range from 1-59°. In the fifth O site, O(5) is bonded to two equivalent Ba(2), two equivalent Ba(3), one Ti(1), and one Ti(2) atom to form a mixture of distorted edge, corner, and face-sharing OBa4Ti2 octahedra. The corner-sharing octahedral tilt angles range from 1-59°. In the sixth O site, O(6) is bonded to two equivalent Ba(2), two equivalent Ba(3), one Ti(3), and one Ti(4) atom to form a mixture of distorted edge, corner, and face-sharing OBa4Ti2 octahedra. The corner-sharing octahedral tilt angles range from 1-59°. In the seventh O site, O(7) is bonded to two equivalent Ba(1), two equivalent Ba(2), one Ti(4), and one Ti(5) atom to form a mixture of distorted edge, corner, and face-sharing OBa4Ti2 octahedra. The corner-sharing octahedral tilt angles range from 1-60°. In the eighth O site, O(8) is bonded to four equivalent Ba(3), one Ti(2), and one Ti(3) atom to form a mixture of distorted edge, corner, and face-sharing OBa4Ti2 octahedra. The corner-sharing octahedral tilt angles range from 1-59°. In the ninth O site, O(9) is bonded to four equivalent Ba(1) and two equivalent Ti(5) atoms to form a mixture of distorted edge, corner, and face-sharing OBa4Ti2 octahedra. The corner-sharing octahedral tilt angles range from 1-59°. In the tenth O site, O(10) is bonded in a distorted linear geometry to two equivalent Ba(1), two equivalent Ba(2), one Ti(1), and one Ti(5) atom. In the eleventh O site, O(11) is bonded in a distorted linear geometry to four equivalent Ba(3) and two equivalent Ti(3) atoms. In the twelfth O site, O(12) is bonded to four equivalent Ba(1) and two equivalent Ti(6) atoms to form a mixture of distorted edge, corner, and face-sharing OBa4Ti2 octahedra. The corner-sharing octahedral tilt angles range from 1-59°.