Materials Data on BaCoAs2O7 by Materials Project
BaCoAs2O7 crystallizes in the triclinic P-1 space group. The structure is three-dimensional. Ba2+ is bonded in a 9-coordinate geometry to nine O2- atoms. There are a spread of Ba–O bond distances ranging from 2.72–3.07 Å. Co2+ is bonded to five O2- atoms to form CoO5 trigonal bipyramids that share corners with five AsO4 tetrahedra and an edgeedge with one CoO5 trigonal bipyramid. There are a spread of Co–O bond distances ranging from 2.02–2.25 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 a cornercorner with one AsO4 tetrahedra and corners with three equivalent CoO5 trigonal bipyramids. There are a spread of As–O bond distances ranging from 1.67–1.80 Å. In the second As5+ site, As5+ is bonded to four O2- atoms to form AsO4 tetrahedra that share a cornercorner with one AsO4 tetrahedra and corners with two equivalent CoO5 trigonal bipyramids. There are a spread of As–O bond distances ranging from 1.69–1.80 Å. There are seven inequivalent O2- sites. In the first O2- site, O2- is bonded in a distorted single-bond geometry to three equivalent Ba2+ and one As5+ atom. In the second O2- site, O2- is bonded in a 2-coordinate geometry to two equivalent Ba2+, one Co2+, and one As5+ atom. In the third O2- site, O2- is bonded in a 3-coordinate geometry to one Ba2+, two equivalent Co2+, and one As5+ atom. In the fourth O2- site, O2- is bonded in a bent 120 degrees geometry to two As5+ atoms. In the fifth O2- site, O2- is bonded in a 3-coordinate geometry to one Ba2+, one Co2+, and one As5+ atom. In the sixth O2- site, O2- is bonded in a distorted bent 120 degrees geometry to one Ba2+, one Co2+, and one As5+ atom. In the seventh O2- site, O2- is bonded in a distorted single-bond geometry to one Ba2+ and one As5+ atom.