DOE OSTI2020
BaSr3(CoO3)4 crystallizes in the monoclinic Pm space group. The structure is three-dimensional. Ba2+ is bonded to twelve O2- atoms to form BaO12 cuboctahedra that share corners with two equivalent BaO12 cuboctahedra, corners with four equivalent SrO12 cuboctahedra, corners with six CoO6 octahedra, faces with two equivalent BaO12 cuboctahedra, faces with six SrO12 cuboctahedra, and faces with six CoO6 octahedra. The corner-sharing octahedra tilt angles range from 14–15°. There are a spread of Ba–O bond distances ranging from 2.77–2.97 Å. There are three inequivalent Sr2+ sites. In the first Sr2+ site, Sr2+ is bonded to twelve O2- atoms to form SrO12 cuboctahedra that share corners with two equivalent SrO12 cuboctahedra, corners with four equivalent BaO12 cuboctahedra, corners with six CoO6 octahedra, faces with eight SrO12 cuboctahedra, and faces with six CoO6 octahedra. The corner-sharing octahedral tilt angles are 15°. There are a spread of Sr–O bond distances ranging from 2.70–2.95 Å. In the second Sr2+ site, Sr2+ is bonded to twelve O2- atoms to form SrO12 cuboctahedra that share corners with six SrO12 cuboctahedra, corners with six CoO6 octahedra, faces with four equivalent BaO12 cuboctahedra, faces with four SrO12 cuboctahedra, and faces with six CoO6 octahedra. The corner-sharing octahedra tilt angles range from 14–16°. There are a spread of Sr–O bond distances ranging from 2.77–2.98 Å. In the third Sr2+ site, Sr2+ is bonded to twelve O2- atoms to form SrO12 cuboctahedra that share corners with six SrO12 cuboctahedra, corners with six CoO6 octahedra, faces with two equivalent BaO12 cuboctahedra, faces with six SrO12 cuboctahedra, and faces with six CoO6 octahedra. The corner-sharing octahedra tilt angles range from 15–16°. There are a spread of Sr–O bond distances ranging from 2.74–2.95 Å. There are two inequivalent Co4+ sites. In the first Co4+ site, Co4+ is bonded to six O2- atoms to form CoO6 octahedra that share corners with two equivalent BaO12 cuboctahedra, corners with four SrO12 cuboctahedra, faces with two equivalent BaO12 cuboctahedra, faces with four SrO12 cuboctahedra, and faces with two equivalent CoO6 octahedra. There are a spread of Co–O bond distances ranging from 1.87–1.90 Å. In the second Co4+ site, Co4+ is bonded to six O2- atoms to form CoO6 octahedra that share a cornercorner with one BaO12 cuboctahedra, corners with five SrO12 cuboctahedra, a faceface with one BaO12 cuboctahedra, faces with five SrO12 cuboctahedra, and faces with two equivalent CoO6 octahedra. There is four shorter (1.88 Å) and two longer (1.90 Å) Co–O bond length. There are twelve inequivalent O2- sites. In the first O2- site, O2- is bonded in a 2-coordinate geometry to two equivalent Ba2+, two Sr2+, and two equivalent Co4+ atoms. In the second O2- site, O2- is bonded in a 2-coordinate geometry to four Sr2+ and two equivalent Co4+ atoms. In the third O2- site, O2- is bonded in a 6-coordinate geometry to two equivalent Ba2+, two Sr2+, and two equivalent Co4+ atoms. In the fourth O2- site, O2- is bonded in a 2-coordinate geometry to four Sr2+ and two equivalent Co4+ atoms. In the fifth O2- site, O2- is bonded in a 2-coordinate geometry to two equivalent Ba2+, two equivalent Sr2+, and two equivalent Co4+ atoms. In the sixth O2- site, O2- is bonded in a 2-coordinate geometry to four Sr2+ and two equivalent Co4+ atoms. In the seventh O2- site, O2- is bonded in a 6-coordinate geometry to one Ba2+, three Sr2+, and two equivalent Co4+ atoms. In the eighth O2- site, O2- is bonded in a 2-coordinate geometry to one Ba2+, three Sr2+, and two equivalent Co4+ atoms. In the ninth O2- site, O2- is bonded in a 2-coordinate geometry to one Ba2+, three Sr2+, and two equivalent Co4+ atoms. In the tenth O2- site, O2- is bonded in a 6-coordinate geometry to one Ba2+, three Sr2+, and two equivalent Co4+ atoms. In the eleventh O2- site, O2- is bonded in a 2-coordinate geometry to two equivalent Ba2+, two equivalent Sr2+, and two equivalent Co4+ atoms. In the twelfth O2- site, O2- is bonded in a 2-coordinate geometry to four Sr2+ and two equivalent Co4+ atoms.