Materials Data on Al2Cr4O19 by Materials Project

Abstract

Cr4Al2O19 crystallizes in the monoclinic P2/c space group. The structure is two-dimensional and consists of one Cr4Al2O19 sheet oriented in the (0, 1, 0) direction. there are two inequivalent Cr sites. In the first Cr site, Cr is bonded to four O atoms to form CrO4 tetrahedra that share corners with three AlO6 octahedra. The corner-sharing octahedra tilt angles range from 30–43°. There are a spread of Cr–O bond distances ranging from 1.59–1.71 Å. In the second Cr site, Cr is bonded to four O atoms to form CrO4 tetrahedra that share a cornercorner with one AlO6 octahedra and a cornercorner with one CrO4 tetrahedra. The corner-sharing octahedral tilt angles are 15°. There are a spread of Cr–O bond distances ranging from 1.60–1.77 Å. There are two inequivalent Al sites. In the first Al site, Al is bonded to six O atoms to form AlO6 octahedra that share corners with four equivalent CrO4 tetrahedra. There are a spread of Al–O bond distances ranging from 1.88–1.90 Å. In the second Al site, Al is bonded to six O atoms to form AlO6 octahedra that share corners with four CrO4 tetrahedra. There are a spread of Al–O bond distances ranging from 1.86–1.91 Å. There are ten inequivalent O sites. In the first O site, O is bonded in a linear geometry to one Cr and one Al atom. In the second O site, O is bonded in a single-bond geometry to one Cr atom. In the third O site, O is bonded in a single-bond geometry to one Al atom. In the fourth O site, O is bonded in a bent 150 degrees geometry to one Cr and one Al atom. In the fifth O site, O is bonded in a single-bond geometry to one Al atom. In the sixth O site, O is bonded in a bent 150 degrees geometry to one Cr and one Al atom. In the seventh O site, O is bonded in a single-bond geometry to one Cr atom. In the eighth O site, O is bonded in a bent 150 degrees geometry to one Cr and one Al atom. In the ninth O site, O is bonded in a distorted bent 120 degrees geometry to two equivalent Cr atoms. In the tenth O site, O is bonded in a single-bond geometry to one Cr atom.