BaTi4O9 crystallizes in the orthorhombic Pmmn space group. Ba(1) is bonded in a 10-coordinate geometry to two equivalent O(1), four equivalent O(2), and four equivalent O(3) atoms. There are two inequivalent Ti sites. In the first Ti site, Ti(1) is bonded to one O(1), one O(2), one O(3), one O(4), and two equivalent O(5) atoms to form corner-sharing TiO6 octahedra. The corner-sharing octahedral tilt angles range from 25-34°. In the second Ti site, Ti(2) is bonded in a 6-coordinate geometry to one O(2), one O(3), one O(5), and three equivalent O(4) atoms. There are five inequivalent O sites. In the first O site, O(1) is bonded in a bent 150 degrees geometry to two equivalent Ba(1) and two equivalent Ti(1) atoms. In the second O site, O(2) is bonded in a distorted linear geometry to two equivalent Ba(1), one Ti(1), and one Ti(2) atom. In the third O site, O(3) is bonded in a distorted water-like geometry to two equivalent Ba(1), one Ti(1), and one Ti(2) atom. In the fourth O site, O(4) is bonded to one Ti(1) and three equivalent Ti(2) atoms to form a mixture of distorted corner and edge-sharing OTi4 trigonal pyramids. In the fifth O site, O(5) is bonded in a distorted T-shaped geometry to one Ti(2) and two equivalent Ti(1) atoms.
BaTi4O9 crystallizes in the orthorhombic Pmmn space group. Ba(1) is bonded in a 10-coordinate geometry to two equivalent O(1), four equivalent O(2), and four equivalent O(3) atoms. Both Ba(1)-O(1) bond lengths are 3.03 Å. All Ba(1)-O(2) bond lengths are 3.10 Å. All Ba(1)-O(3) bond lengths are 2.85 Å. There are two inequivalent Ti sites. In the first Ti site, Ti(1) is bonded to one O(1), one O(2), one O(3), one O(4), and two equivalent O(5) atoms to form corner-sharing TiO6 octahedra. The corner-sharing octahedral tilt angles range from 25-34°. The Ti(1)-O(1) bond length is 1.86 Å. The Ti(1)-O(2) bond length is 2.01 Å. The Ti(1)-O(3) bond length is 1.91 Å. The Ti(1)-O(4) bond length is 2.12 Å. Both Ti(1)-O(5) bond lengths are 1.95 Å. In the second Ti site, Ti(2) is bonded in a 6-coordinate geometry to one O(2), one O(3), one O(5), and three equivalent O(4) atoms. The Ti(2)-O(2) bond length is 1.76 Å. The Ti(2)-O(3) bond length is 1.91 Å. The Ti(2)-O(5) bond length is 2.04 Å. There are two shorter (1.96 Å) and one longer (2.29 Å) Ti(2)-O(4) bond length. There are five inequivalent O sites. In the first O site, O(1) is bonded in a bent 150 degrees geometry to two equivalent Ba(1) and two equivalent Ti(1) atoms. In the second O site, O(2) is bonded in a distorted linear geometry to two equivalent Ba(1), one Ti(1), and one Ti(2) atom. In the third O site, O(3) is bonded in a distorted water-like geometry to two equivalent Ba(1), one Ti(1), and one Ti(2) atom. In the fourth O site, O(4) is bonded to one Ti(1) and three equivalent Ti(2) atoms to form a mixture of distorted corner and edge-sharing OTi4 trigonal pyramids. In the fifth O site, O(5) is bonded in a distorted T-shaped geometry to one Ti(2) and two equivalent Ti(1) atoms.