DOI: 10.17188/1301581
title: Materials Data on Ba8Ta7O24 by Materials Project

description: Ba8Ta7O24 crystallizes in the trigonal P3m1 space group. The structure is three-dimensional. there are eight inequivalent Ba2+ sites. In the first Ba2+ site, Ba2+ is bonded to twelve O2- atoms to form BaO12 cuboctahedra that share corners with nine BaO12 cuboctahedra, faces with six BaO12 cuboctahedra, and faces with eight TaO6 octahedra. There are three shorter (2.88 Å) and nine longer (2.96 Å) Ba–O bond lengths. In the second Ba2+ site, Ba2+ is bonded in a 9-coordinate geometry to nine O2- atoms. There are three shorter (2.78 Å) and six longer (3.02 Å) Ba–O bond lengths. In the third Ba2+ site, Ba2+ is bonded in a 12-coordinate geometry to twelve O2- atoms. There are a spread of Ba–O bond distances ranging from 2.63–3.27 Å. In the fourth Ba2+ site, Ba2+ is bonded to twelve O2- atoms to form BaO12 cuboctahedra that share corners with twelve BaO12 cuboctahedra, faces with six BaO12 cuboctahedra, and faces with eight TaO6 octahedra. There are a spread of Ba–O bond distances ranging from 2.82–2.98 Å. In the fifth Ba2+ site, Ba2+ is bonded to twelve O2- atoms to form distorted BaO12 cuboctahedra that share corners with nine BaO12 cuboctahedra, faces with six BaO12 cuboctahedra, and faces with seven TaO6 octahedra. There are a spread of Ba–O bond distances ranging from 2.69–3.11 Å. In the sixth Ba2+ site, Ba2+ is bonded to twelve O2- atoms to form BaO12 cuboctahedra that share corners with six equivalent BaO12 cuboctahedra, corners with three equivalent TaO6 octahedra, faces with four BaO12 cuboctahedra, and faces with seven TaO6 octahedra. The corner-sharing octahedral tilt angles are 14°. There are a spread of Ba–O bond distances ranging from 2.88–2.96 Å. In the seventh Ba2+ site, Ba2+ is bonded to twelve O2- atoms to form distorted BaO12 cuboctahedra that share corners with nine BaO12 cuboctahedra, faces with three equivalent BaO12 cuboctahedra, and faces with five TaO6 octahedra. There are a spread of Ba–O bond distances ranging from 2.89–3.15 Å. In the eighth Ba2+ site, Ba2+ is bonded to twelve O2- atoms to form BaO12 cuboctahedra that share corners with nine BaO12 cuboctahedra, corners with three equivalent TaO6 octahedra, faces with seven BaO12 cuboctahedra, and faces with seven TaO6 octahedra. The corner-sharing octahedral tilt angles are 13°. There are a spread of Ba–O bond distances ranging from 2.84–3.06 Å. There are seven inequivalent Ta+4.57+ sites. In the first Ta+4.57+ site, Ta+4.57+ is bonded to six O2- atoms to form TaO6 octahedra that share corners with six TaO6 octahedra and faces with four BaO12 cuboctahedra. The corner-sharing octahedra tilt angles range from 6–8°. There are three shorter (1.96 Å) and three longer (2.10 Å) Ta–O bond lengths. In the second Ta+4.57+ site, Ta+4.57+ is bonded to six O2- atoms to form TaO6 octahedra that share corners with three equivalent BaO12 cuboctahedra, corners with three equivalent TaO6 octahedra, faces with six BaO12 cuboctahedra, and a faceface with one TaO6 octahedra. The corner-sharing octahedral tilt angles are 6°. There are three shorter (2.05 Å) and three longer (2.09 Å) Ta–O bond lengths. In the third Ta+4.57+ site, Ta+4.57+ is bonded to six O2- atoms to form TaO6 octahedra that share corners with three equivalent BaO12 cuboctahedra, corners with three equivalent TaO6 octahedra, faces with seven BaO12 cuboctahedra, and a faceface with one TaO6 octahedra. The corner-sharing octahedral tilt angles are 2°. There are three shorter (2.07 Å) and three longer (2.10 Å) Ta–O bond lengths. In the fourth Ta+4.57+ site, Ta+4.57+ is bonded to six O2- atoms to form TaO6 octahedra that share corners with three equivalent TaO6 octahedra and faces with seven BaO12 cuboctahedra. The corner-sharing octahedral tilt angles are 7°. There are three shorter (1.88 Å) and three longer (2.26 Å) Ta–O bond lengths. In the fifth Ta+4.57+ site, Ta+4.57+ is bonded to six O2- atoms to form TaO6 octahedra that share corners with six TaO6 octahedra and faces with eight BaO12 cuboctahedra. The corner-sharing octahedral tilt angles are 2°. There are three shorter (2.05 Å) and three longer (2.06 Å) Ta–O bond lengths. In the sixth Ta+4.57+ site, Ta+4.57+ is bonded to six O2- atoms to form TaO6 octahedra that share corners with six TaO6 octahedra and faces with eight BaO12 cuboctahedra. The corner-sharing octahedra tilt angles range from 2–7°. There are three shorter (2.00 Å) and three longer (2.10 Å) Ta–O bond lengths. In the seventh Ta+4.57+ site, Ta+4.57+ is bonded to six O2- atoms to form TaO6 octahedra that share corners with three equivalent TaO6 octahedra and faces with two BaO12 cuboctahedra. The corner-sharing octahedral tilt angles are 8°. There are three shorter (1.88 Å) and three longer (2.22 Å) Ta–O bond lengths. There are eight inequivalent O2- sites. In the first O2- site, O2- is bonded in a distorted single-bond geometry to four Ba2+ and one Ta+4.57+ atom. In the second O2- site, O2- is bonded in a 2-coordinate geometry to three Ba2+ and two Ta+4.57+ atoms. In the third O2- site, O2- is bonded in a distorted linear geometry to four Ba2+ and two Ta+4.57+ atoms. In the fourth O2- site, O2- is bonded in a distorted linear geometry to four Ba2+ and two Ta+4.57+ atoms. In the fifth O2- site, O2- is bonded in a distorted linear geometry to four Ba2+ and two Ta+4.57+ atoms. In the sixth O2- site, O2- is bonded in a 6-coordinate geometry to four Ba2+ and two Ta+4.57+ atoms. In the seventh O2- site, O2- is bonded in a 2-coordinate geometry to four Ba2+ and two Ta+4.57+ atoms. In the eighth O2- site, O2- is bonded in a distorted single-bond geometry to four Ba2+ and one Ta+4.57+ atom.