Materials Data on Ba2Ta2O7 by Materials Project

Abstract

Ba2Ta2O7 crystallizes in the orthorhombic Cmcm space group. The structure is three-dimensional. there are two inequivalent Ba2+ sites. In the first Ba2+ site, Ba2+ is bonded in a 6-coordinate geometry to six equivalent O2- atoms. There are four shorter (2.60 Å) and two longer (2.78 Å) Ba–O bond lengths. In the second Ba2+ site, Ba2+ is bonded to twelve O2- atoms to form BaO12 cuboctahedra that share corners with six equivalent BaO12 cuboctahedra, faces with four equivalent BaO12 cuboctahedra, and faces with eight TaO6 octahedra. There are a spread of Ba–O bond distances ranging from 2.74–2.97 Å. There are two inequivalent Ta5+ sites. In the first Ta5+ site, Ta5+ is bonded to six O2- atoms to form TaO6 octahedra that share corners with four TaO6 octahedra and faces with two equivalent BaO12 cuboctahedra. The corner-sharing octahedra tilt angles range from 8–13°. There are a spread of Ta–O bond distances ranging from 1.86–2.23 Å. In the second Ta5+ site, Ta5+ is bonded to six O2- atoms to form TaO6 octahedra that share corners with six TaO6 octahedra and faces with six equivalent BaO12 cuboctahedra. The corner-sharing octahedra tilt angles range from 0–10°. There are a spread of Ta–O bond distances ranging from 1.93–2.15 Å. There are five inequivalent O2- sites. In the first O2- site, O2- is bonded in a distorted linear geometry to four equivalent Ba2+ and two equivalent Ta5+ atoms. In the second O2- site, O2- is bonded in a 4-coordinate geometry to two equivalent Ba2+ and two Ta5+ atoms. In the third O2- site, O2- is bonded in a 4-coordinate geometry to three equivalent Ba2+ and one Ta5+ atom. In the fourth O2- site, O2- is bonded in a distorted linear geometry to three equivalent Ba2+ and two equivalent Ta5+ atoms. In the fifth O2- site, O2- is bonded in a 3-coordinate geometry to one Ba2+ and two equivalent Ta5+ atoms.