Materials Data on Cr8O21 by Materials Project
Cr8O21 crystallizes in the triclinic P-1 space group. The structure is three-dimensional. there are four inequivalent Cr+5.25+ sites. In the first Cr+5.25+ site, Cr+5.25+ is bonded to four O2- atoms to form corner-sharing CrO4 tetrahedra. There are a spread of Cr–O bond distances ranging from 1.59–1.78 Å. In the second Cr+5.25+ site, Cr+5.25+ is bonded to six O2- atoms to form CrO6 octahedra that share corners with six CrO4 tetrahedra and an edgeedge with one CrO6 octahedra. There are a spread of Cr–O bond distances ranging from 1.96–2.08 Å. In the third Cr+5.25+ site, Cr+5.25+ is bonded to four O2- atoms to form CrO4 tetrahedra that share corners with two equivalent CrO6 octahedra and a cornercorner with one CrO4 tetrahedra. The corner-sharing octahedra tilt angles range from 18–39°. There are a spread of Cr–O bond distances ranging from 1.67–1.81 Å. In the fourth Cr+5.25+ site, Cr+5.25+ is bonded to four O2- atoms to form distorted corner-sharing CrO4 tetrahedra. The corner-sharing octahedra tilt angles range from 21–58°. There are a spread of Cr–O bond distances ranging from 1.67–1.85 Å. There are eleven inequivalent O2- sites. In the first O2- site, O2- is bonded in a distorted trigonal planar geometry to three Cr+5.25+ atoms. In the second O2- site, O2- is bonded in a distorted single-bond geometry to one Cr+5.25+ atom. In the third O2- site, O2- is bonded in a bent 150 degrees geometry to two Cr+5.25+ atoms. In the fourth O2- site, O2- is bonded in a bent 150 degrees geometry to two Cr+5.25+ atoms. In the fifth O2- site, O2- is bonded in a single-bond geometry to one Cr+5.25+ atom. In the sixth O2- site, O2- is bonded in a bent 150 degrees geometry to two Cr+5.25+ atoms. In the seventh O2- site, O2- is bonded in a distorted linear geometry to two Cr+5.25+ atoms. In the eighth O2- site, O2- is bonded in a single-bond geometry to one Cr+5.25+ atom. In the ninth O2- site, O2- is bonded in a distorted single-bond geometry to one Cr+5.25+ atom. In the tenth O2- site, O2- is bonded in a linear geometry to two equivalent Cr+5.25+ atoms. In the eleventh O2- site, O2- is bonded in a bent 150 degrees geometry to two Cr+5.25+ atoms.