Ba3Ti2O7 crystallizes in the orthorhombic Fmm2 space group. There are two inequivalent Ba sites. In the first Ba site, Ba(1) is bonded in a 9-coordinate geometry to four equivalent O(2) and five equivalent O(1) atoms. In the second Ba site, Ba(2) is bonded to four equivalent O(3) and eight equivalent O(2) atoms to form BaO12 cuboctahedra that share corners with four equivalent Ba(2)O12 cuboctahedra, faces with four equivalent Ba(2)O12 cuboctahedra, and faces with eight equivalent Ti(1)O6 octahedra. Ti(1) is bonded to one O(1), one O(3), and four equivalent O(2) atoms to form TiO6 octahedra that share corners with five equivalent Ti(1)O6 octahedra and faces with four equivalent Ba(2)O12 cuboctahedra. The corner-sharing octahedral tilt angles range from 5-8°. There are three inequivalent O sites. In the first O site, O(1) is bonded to five equivalent Ba(1) and one Ti(1) atom to form a mixture of distorted corner and edge-sharing OBa5Ti octahedra. The corner-sharing octahedral tilt angles are 3°. In the second O site, O(2) is bonded in a 6-coordinate geometry to two equivalent Ba(1), two equivalent Ba(2), and two equivalent Ti(1) atoms. In the third O site, O(3) is bonded in a distorted linear geometry to four equivalent Ba(2) and two equivalent Ti(1) atoms.
Ba3Ti2O7 crystallizes in the orthorhombic Fmm2 space group. There are two inequivalent Ba sites. In the first Ba site, Ba(1) is bonded in a 9-coordinate geometry to four equivalent O(2) and five equivalent O(1) atoms. There are two shorter (2.77 Å) and two longer (2.81 Å) Ba(1)-O(2) bond lengths. There are a spread of Ba(1)-O(1) bond distances ranging from 2.82-2.94 Å. In the second Ba site, Ba(2) is bonded to four equivalent O(3) and eight equivalent O(2) atoms to form BaO12 cuboctahedra that share corners with four equivalent Ba(2)O12 cuboctahedra, faces with four equivalent Ba(2)O12 cuboctahedra, and faces with eight equivalent Ti(1)O6 octahedra. There are a spread of Ba(2)-O(3) bond distances ranging from 2.82-2.95 Å. There are four shorter (2.84 Å) and four longer (2.89 Å) Ba(2)-O(2) bond lengths. Ti(1) is bonded to one O(1), one O(3), and four equivalent O(2) atoms to form TiO6 octahedra that share corners with five equivalent Ti(1)O6 octahedra and faces with four equivalent Ba(2)O12 cuboctahedra. The corner-sharing octahedral tilt angles range from 5-8°. The Ti(1)-O(1) bond length is 1.96 Å. The Ti(1)-O(3) bond length is 2.04 Å. There are two shorter (1.90 Å) and two longer (2.18 Å) Ti(1)-O(2) bond lengths. There are three inequivalent O sites. In the first O site, O(1) is bonded to five equivalent Ba(1) and one Ti(1) atom to form a mixture of distorted corner and edge-sharing OBa5Ti octahedra. The corner-sharing octahedral tilt angles are 3°. In the second O site, O(2) is bonded in a 6-coordinate geometry to two equivalent Ba(1), two equivalent Ba(2), and two equivalent Ti(1) atoms. In the third O site, O(3) is bonded in a distorted linear geometry to four equivalent Ba(2) and two equivalent Ti(1) atoms.