Materials Data on Cr2As6O19 by Materials Project
Cr2As6O19 crystallizes in the orthorhombic Pmmn space group. The structure is three-dimensional. Cr4+ is bonded to six O2- atoms to form CrO6 octahedra that share corners with six AsO4 tetrahedra. There are a spread of Cr–O bond distances ranging from 1.98–2.00 Å. There are two inequivalent As5+ sites. In the first As5+ site, As5+ is bonded to four O2- atoms to form AsO4 tetrahedra that share corners with two equivalent CrO6 octahedra and corners with two equivalent AsO4 tetrahedra. The corner-sharing octahedra tilt angles range from 47–53°. There is two shorter (1.68 Å) and two longer (1.78 Å) As–O bond length. In the second As5+ site, As5+ is bonded to four O2- atoms to form AsO4 tetrahedra that share corners with two equivalent CrO6 octahedra and a cornercorner with one AsO4 tetrahedra. The corner-sharing octahedral tilt angles are 48°. There are a spread of As–O bond distances ranging from 1.72–1.78 Å. There are seven inequivalent O2- sites. In the first O2- site, O2- is bonded in a bent 120 degrees geometry to two equivalent As5+ atoms. In the second O2- site, O2- is bonded in a bent 120 degrees geometry to one Cr4+ and one As5+ atom. In the third O2- site, O2- is bonded in a bent 120 degrees geometry to two equivalent As5+ atoms. In the fourth O2- site, O2- is bonded in a bent 120 degrees geometry to two equivalent As5+ atoms. In the fifth O2- site, O2- is bonded in a single-bond geometry to one As5+ atom. In the sixth O2- site, O2- is bonded in a distorted bent 120 degrees geometry to one Cr4+ and one As5+ atom. In the seventh O2- site, O2- is bonded in a distorted bent 120 degrees geometry to one Cr4+ and one As5+ atom.