Materials Data on Co2As2O9 by Materials Project
Co2As2O9 crystallizes in the monoclinic P2_1/c space group. The structure is three-dimensional. there are two inequivalent Co4+ sites. In the first Co4+ site, Co4+ is bonded to six O2- atoms to form distorted CoO6 octahedra that share corners with five AsO4 tetrahedra and edges with two equivalent CoO6 octahedra. There are a spread of Co–O bond distances ranging from 1.61–2.19 Å. In the second Co4+ site, Co4+ is bonded to six O2- atoms to form distorted CoO6 octahedra that share corners with five AsO4 tetrahedra and edges with two equivalent CoO6 octahedra. There are a spread of Co–O bond distances ranging from 1.72–2.27 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 five CoO6 octahedra and a cornercorner with one AsO4 tetrahedra. The corner-sharing octahedra tilt angles range from 51–62°. There are a spread of As–O bond distances ranging from 1.69–1.80 Å. In the second As5+ site, As5+ is bonded to four O2- atoms to form AsO4 tetrahedra that share corners with five CoO6 octahedra and a cornercorner with one AsO4 tetrahedra. The corner-sharing octahedra tilt angles range from 47–61°. There are a spread of As–O bond distances ranging from 1.69–1.78 Å. There are nine inequivalent O2- sites. In the first O2- site, O2- is bonded in a bent 120 degrees geometry to one Co4+ and one As5+ atom. In the second O2- site, O2- is bonded in a distorted trigonal planar geometry to two Co4+ and one As5+ atom. In the third O2- site, O2- is bonded in a distorted trigonal planar geometry to two Co4+ and one As5+ atom. In the fourth O2- site, O2- is bonded in a single-bond geometry to one Co4+ atom. In the fifth O2- site, O2- is bonded in a 3-coordinate geometry to two Co4+ and one As5+ atom. In the sixth O2- site, O2- is bonded in a single-bond geometry to one Co4+ atom. In the seventh O2- site, O2- is bonded in a bent 120 degrees geometry to one Co4+ and one As5+ atom. In the eighth O2- site, O2- is bonded in a distorted trigonal planar geometry to two Co4+ and one As5+ atom. In the ninth O2- site, O2- is bonded in a bent 120 degrees geometry to two As5+ atoms.