DOE OSTI2020
Sr3CaIr2O9 is Orthorhombic Perovskite-derived structured and crystallizes in the monoclinic P2_1/c space group. The structure is three-dimensional. there are three inequivalent Sr2+ sites. In the first Sr2+ site, Sr2+ is bonded in a 8-coordinate geometry to eight O2- atoms. There are a spread of Sr–O bond distances ranging from 2.52–2.88 Å. In the second Sr2+ site, Sr2+ is bonded in a 9-coordinate geometry to eight O2- atoms. There are a spread of Sr–O bond distances ranging from 2.55–2.88 Å. In the third Sr2+ site, Sr2+ is bonded in a 8-coordinate geometry to eight O2- atoms. There are a spread of Sr–O bond distances ranging from 2.52–2.90 Å. There are two inequivalent Ca2+ sites. In the first Ca2+ site, Ca2+ is bonded to six O2- atoms to form CaO6 octahedra that share corners with six equivalent IrO6 octahedra. The corner-sharing octahedra tilt angles range from 21–24°. There are four shorter (2.26 Å) and two longer (2.27 Å) Ca–O bond lengths. In the second Ca2+ site, Ca2+ is bonded to six O2- atoms to form CaO6 octahedra that share corners with six equivalent IrO6 octahedra. The corner-sharing octahedra tilt angles range from 20–24°. There are a spread of Ca–O bond distances ranging from 2.24–2.28 Å. There are two inequivalent Ir5+ sites. In the first Ir5+ site, Ir5+ is bonded to six O2- atoms to form IrO6 octahedra that share corners with three equivalent CaO6 octahedra and corners with three equivalent IrO6 octahedra. The corner-sharing octahedra tilt angles range from 21–26°. There are a spread of Ir–O bond distances ranging from 1.94–2.06 Å. In the second Ir5+ site, Ir5+ is bonded to six O2- atoms to form IrO6 octahedra that share corners with three equivalent CaO6 octahedra and corners with three equivalent IrO6 octahedra. The corner-sharing octahedra tilt angles range from 20–26°. There are a spread of Ir–O bond distances ranging from 1.94–2.07 Å. There are nine inequivalent O2- sites. In the first O2- site, O2- is bonded in a 5-coordinate geometry to three Sr2+, one Ca2+, and one Ir5+ atom. In the second O2- site, O2- is bonded in a 5-coordinate geometry to three equivalent Sr2+, one Ca2+, and one Ir5+ atom. In the third O2- site, O2- is bonded in a 5-coordinate geometry to three Sr2+, one Ca2+, and one Ir5+ atom. In the fourth O2- site, O2- is bonded in a 5-coordinate geometry to three Sr2+ and two Ir5+ atoms. In the fifth O2- site, O2- is bonded in a 5-coordinate geometry to three Sr2+ and two Ir5+ atoms. In the sixth O2- site, O2- is bonded in a 5-coordinate geometry to three Sr2+, one Ca2+, and one Ir5+ atom. In the seventh O2- site, O2- is bonded in a 4-coordinate geometry to two equivalent Sr2+, one Ca2+, and one Ir5+ atom. In the eighth O2- site, O2- is bonded in a 4-coordinate geometry to two Sr2+ and two Ir5+ atoms. In the ninth O2- site, O2- is bonded in a 4-coordinate geometry to two Sr2+, one Ca2+, and one Ir5+ atom.