DOI: 10.17188/1746262
title: Materials Data on Al7Cr(Bi2O9)2 by Materials Project

description: CrAl7(Bi2O9)2 crystallizes in the monoclinic P2 space group. The structure is three-dimensional. Cr3+ is bonded to six O2- atoms to form CrO6 octahedra that share corners with four AlO4 tetrahedra and edges with two equivalent AlO6 octahedra. There are a spread of Cr–O bond distances ranging from 1.98–2.04 Å. There are five inequivalent Al3+ sites. In the first Al3+ site, Al3+ is bonded to six O2- atoms to form AlO6 octahedra that share corners with four AlO4 tetrahedra and edges with two equivalent AlO6 octahedra. There is two shorter (1.89 Å) and four longer (1.97 Å) Al–O bond length. In the second Al3+ site, Al3+ is bonded to six O2- atoms to form AlO6 octahedra that share corners with four AlO4 tetrahedra and edges with two equivalent CrO6 octahedra. There are a spread of Al–O bond distances ranging from 1.87–1.98 Å. In the third Al3+ site, Al3+ is bonded to six O2- atoms to form AlO6 octahedra that share corners with four AlO4 tetrahedra and edges with two equivalent AlO6 octahedra. There are a spread of Al–O bond distances ranging from 1.89–1.96 Å. In the fourth Al3+ site, Al3+ is bonded to four O2- atoms to form AlO4 tetrahedra that share a cornercorner with one CrO6 octahedra, corners with three AlO6 octahedra, and a cornercorner with one AlO4 tetrahedra. The corner-sharing octahedra tilt angles range from 48–58°. There are a spread of Al–O bond distances ranging from 1.76–1.81 Å. In the fifth Al3+ site, Al3+ is bonded to four O2- atoms to form AlO4 tetrahedra that share a cornercorner with one CrO6 octahedra, corners with three AlO6 octahedra, and a cornercorner with one AlO4 tetrahedra. The corner-sharing octahedra tilt angles range from 45–58°. There are a spread of Al–O bond distances ranging from 1.76–1.81 Å. There are two inequivalent Bi3+ sites. In the first Bi3+ site, Bi3+ is bonded in a 6-coordinate geometry to six O2- atoms. There are a spread of Bi–O bond distances ranging from 2.18–2.92 Å. In the second Bi3+ site, Bi3+ is bonded in a 6-coordinate geometry to six O2- atoms. There are a spread of Bi–O bond distances ranging from 2.19–2.93 Å. There are ten inequivalent O2- sites. In the first O2- site, O2- is bonded in a 3-coordinate geometry to one Cr3+, one Al3+, and two Bi3+ atoms. In the second O2- site, O2- is bonded in a 3-coordinate geometry to two Al3+ and two Bi3+ atoms. In the third O2- site, O2- is bonded in a 3-coordinate geometry to two Al3+ and two Bi3+ atoms. In the fourth O2- site, O2- is bonded in a 3-coordinate geometry to two Al3+ and two Bi3+ atoms. In the fifth O2- site, O2- is bonded in a linear geometry to two equivalent Al3+ atoms. In the sixth O2- site, O2- is bonded in a linear geometry to two equivalent Al3+ atoms. In the seventh O2- site, O2- is bonded in a distorted trigonal planar geometry to three Al3+ atoms. In the eighth O2- site, O2- is bonded in a distorted trigonal planar geometry to one Cr3+ and two Al3+ atoms. In the ninth O2- site, O2- is bonded in a 4-coordinate geometry to two Al3+ and two Bi3+ atoms. In the tenth O2- site, O2- is bonded in a 4-coordinate geometry to one Cr3+, one Al3+, and two Bi3+ atoms.