Materials Data on Ba3Ti2O7 by Materials Project
Ba3Ti2O7 crystallizes in the monoclinic Cm space group. The structure is three-dimensional. there are three inequivalent Ba2+ sites. In the first Ba2+ site, Ba2+ is bonded in a 9-coordinate geometry to nine O2- atoms. There are a spread of Ba–O bond distances ranging from 2.77–2.94 Å. In the second Ba2+ site, Ba2+ is bonded to twelve O2- atoms to form BaO12 cuboctahedra that share corners with four equivalent BaO12 cuboctahedra, faces with four equivalent BaO12 cuboctahedra, and faces with eight TiO6 octahedra. There are a spread of Ba–O bond distances ranging from 2.82–2.95 Å. In the third Ba2+ site, Ba2+ is bonded in a 9-coordinate geometry to nine O2- atoms. There are a spread of Ba–O bond distances ranging from 2.76–2.94 Å. There are two inequivalent Ti4+ sites. In the first Ti4+ site, Ti4+ is bonded to six O2- atoms to form TiO6 octahedra that share corners with five TiO6 octahedra and faces with four equivalent BaO12 cuboctahedra. The corner-sharing octahedra tilt angles range from 5–8°. There are a spread of Ti–O bond distances ranging from 1.90–2.18 Å. In the second Ti4+ site, Ti4+ is bonded to six O2- atoms to form TiO6 octahedra that share corners with five TiO6 octahedra and faces with four equivalent BaO12 cuboctahedra. The corner-sharing octahedra tilt angles range from 6–8°. There are a spread of Ti–O bond distances ranging from 1.90–2.18 Å. There are four inequivalent O2- sites. In the first O2- site, O2- is bonded in a 6-coordinate geometry to five Ba2+ and one Ti4+ atom. In the second O2- site, O2- is bonded in a 2-coordinate geometry to four Ba2+ and two equivalent Ti4+ atoms. In the third O2- site, O2- is bonded in a 2-coordinate geometry to four Ba2+ and two equivalent Ti4+ atoms. In the fourth O2- site, O2- is bonded in a distorted linear geometry to four equivalent Ba2+ and two Ti4+ atoms.