DOI: 10.17188/1271755
title: Materials Data on Ba4Al2O7 by Materials Project

description: Ba4Al2O7 crystallizes in the orthorhombic Cmce space group. The structure is three-dimensional. there are seven inequivalent Ba2+ sites. In the first Ba2+ site, Ba2+ is bonded in a 7-coordinate geometry to seven O2- atoms. There are a spread of Ba–O bond distances ranging from 2.71–3.23 Å. In the second Ba2+ site, Ba2+ is bonded to six O2- atoms to form distorted BaO6 octahedra that share corners with six AlO4 tetrahedra, an edgeedge with one BaO6 octahedra, and edges with two equivalent BaO7 pentagonal bipyramids. There are a spread of Ba–O bond distances ranging from 2.65–2.79 Å. In the third Ba2+ site, Ba2+ is bonded to seven O2- atoms to form distorted BaO7 pentagonal bipyramids that share corners with two equivalent BaO8 hexagonal bipyramids, corners with three AlO4 tetrahedra, edges with two equivalent BaO6 octahedra, edges with two equivalent AlO4 tetrahedra, and a faceface with one BaO6 octahedra. There are a spread of Ba–O bond distances ranging from 2.56–3.17 Å. In the fourth 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 2.83–3.34 Å. In the fifth Ba2+ site, Ba2+ is bonded to six O2- atoms to form distorted BaO6 octahedra that share corners with six AlO4 tetrahedra, faces with two equivalent BaO8 hexagonal bipyramids, and a faceface with one BaO7 pentagonal bipyramid. There are a spread of Ba–O bond distances ranging from 2.59–2.74 Å. In the sixth Ba2+ site, Ba2+ is bonded to eight O2- atoms to form distorted BaO8 hexagonal bipyramids that share corners with two equivalent BaO8 hexagonal bipyramids, corners with two equivalent BaO7 pentagonal bipyramids, corners with two equivalent AlO4 tetrahedra, edges with four AlO4 tetrahedra, and faces with two equivalent BaO6 octahedra. There are a spread of Ba–O bond distances ranging from 2.69–2.98 Å. In the seventh Ba2+ site, Ba2+ is bonded in a 8-coordinate geometry to eight O2- atoms. There are a spread of Ba–O bond distances ranging from 2.60–3.34 Å. There are three inequivalent Al3+ sites. In the first Al3+ site, Al3+ is bonded to four O2- atoms to form AlO4 tetrahedra that share a cornercorner with one BaO6 octahedra, a cornercorner with one BaO7 pentagonal bipyramid, corners with two equivalent AlO4 tetrahedra, and edges with two equivalent BaO8 hexagonal bipyramids. The corner-sharing octahedral tilt angles are 25°. There are a spread of Al–O bond distances ranging from 1.75–1.78 Å. In the second Al3+ site, Al3+ is bonded to four O2- atoms to form AlO4 tetrahedra that share a cornercorner with one BaO8 hexagonal bipyramid, corners with three BaO6 octahedra, a cornercorner with one AlO4 tetrahedra, an edgeedge with one BaO8 hexagonal bipyramid, and an edgeedge with one BaO7 pentagonal bipyramid. The corner-sharing octahedra tilt angles range from 9–46°. There are a spread of Al–O bond distances ranging from 1.77–1.80 Å. In the third Al3+ site, Al3+ is bonded to four O2- atoms to form AlO4 tetrahedra that share corners with five BaO6 octahedra and corners with two equivalent BaO7 pentagonal bipyramids. The corner-sharing octahedra tilt angles range from 2–66°. There are a spread of Al–O bond distances ranging from 1.78–1.82 Å. There are nine inequivalent O2- sites. In the first O2- site, O2- is bonded in a 1-coordinate geometry to five Ba2+ and one Al3+ atom. In the second O2- site, O2- is bonded in a 4-coordinate geometry to three Ba2+ and one Al3+ atom. In the third O2- site, O2- is bonded in a 6-coordinate geometry to five Ba2+ and one Al3+ atom. In the fourth O2- site, O2- is bonded in a 1-coordinate geometry to four Ba2+ and one Al3+ atom. In the fifth O2- site, O2- is bonded in a 1-coordinate geometry to four Ba2+ and one Al3+ atom. In the sixth O2- site, O2- is bonded in a 1-coordinate geometry to five Ba2+ and one Al3+ atom. In the seventh O2- site, O2- is bonded in a 1-coordinate geometry to four Ba2+ and one Al3+ atom. In the eighth O2- site, O2- is bonded in a distorted single-bond geometry to three Ba2+ and one Al3+ atom. In the ninth O2- site, O2- is bonded in a distorted linear geometry to four Ba2+ and two Al3+ atoms.