DOI: 10.17188/1281204
title: Materials Data on Ca2(Fe2O3)11 by Materials Project

description: Ca2Fe22O33 crystallizes in the trigonal R32 space group. The structure is three-dimensional. Ca2+ is bonded in a 6-coordinate geometry to six O2- atoms. There are three shorter (2.32 Å) and three longer (2.51 Å) Ca–O bond lengths. There are eight inequivalent Fe+2.82+ sites. In the first Fe+2.82+ site, Fe+2.82+ is bonded to six O2- atoms to form FeO6 octahedra that share corners with six FeO4 tetrahedra and edges with six FeO6 octahedra. There are four shorter (2.14 Å) and two longer (2.15 Å) Fe–O bond lengths. In the second Fe+2.82+ site, Fe+2.82+ is bonded to six O2- atoms to form FeO6 octahedra that share corners with three FeO4 tetrahedra, a cornercorner with one FeO5 trigonal bipyramid, and edges with six FeO6 octahedra. There are a spread of Fe–O bond distances ranging from 1.95–2.11 Å. In the third Fe+2.82+ site, Fe+2.82+ is bonded to six O2- atoms to form FeO6 octahedra that share corners with six FeO4 tetrahedra and edges with six FeO6 octahedra. There are three shorter (2.01 Å) and three longer (2.09 Å) Fe–O bond lengths. In the fourth Fe+2.82+ site, Fe+2.82+ is bonded to four O2- atoms to form corner-sharing FeO4 tetrahedra. The corner-sharing octahedra tilt angles range from 54–60°. There is one shorter (1.84 Å) and three longer (1.98 Å) Fe–O bond length. In the fifth Fe+2.82+ site, Fe+2.82+ is bonded to four O2- atoms to form corner-sharing FeO4 tetrahedra. The corner-sharing octahedra tilt angles range from 53–58°. There is three shorter (1.91 Å) and one longer (1.93 Å) Fe–O bond length. In the sixth Fe+2.82+ site, Fe+2.82+ is bonded to five O2- atoms to form FeO5 trigonal bipyramids that share corners with two equivalent FeO6 octahedra, corners with six equivalent FeO5 trigonal bipyramids, and edges with two equivalent FeO5 trigonal bipyramids. The corner-sharing octahedral tilt angles are 58°. There are three shorter (2.01 Å) and two longer (2.04 Å) Fe–O bond lengths. In the seventh Fe+2.82+ site, Fe+2.82+ is bonded to six O2- atoms to form distorted FeO6 octahedra that share corners with six FeO5 trigonal bipyramids and edges with three equivalent FeO6 octahedra. There are three shorter (2.04 Å) and three longer (2.10 Å) Fe–O bond lengths. In the eighth Fe+2.82+ site, Fe+2.82+ is bonded to five O2- atoms to form FeO5 trigonal bipyramids that share corners with six FeO6 octahedra and edges with three equivalent FeO5 trigonal bipyramids. The corner-sharing octahedra tilt angles range from 57–58°. There are a spread of Fe–O bond distances ranging from 1.96–2.13 Å. There are nine inequivalent O2- sites. In the first O2- site, O2- is bonded in a distorted rectangular see-saw-like geometry to four Fe+2.82+ atoms. In the second O2- site, O2- is bonded in a rectangular see-saw-like geometry to four Fe+2.82+ atoms. In the third O2- site, O2- is bonded to four Fe+2.82+ atoms to form OFe4 trigonal pyramids that share corners with three equivalent OCaFe3 tetrahedra, corners with four OFe4 trigonal pyramids, and edges with three equivalent OCaFe3 tetrahedra. In the fourth O2- site, O2- is bonded to one Ca2+ and three Fe+2.82+ atoms to form distorted OCaFe3 trigonal pyramids that share corners with four equivalent OCaFe3 tetrahedra, corners with eight OFe4 trigonal pyramids, an edgeedge with one OCaFe3 tetrahedra, and edges with two equivalent OCaFe3 trigonal pyramids. In the fifth O2- site, O2- is bonded in a rectangular see-saw-like geometry to four Fe+2.82+ atoms. In the sixth O2- site, O2- is bonded to one Ca2+ and three Fe+2.82+ atoms to form distorted OCaFe3 tetrahedra that share corners with seven equivalent OCaFe3 tetrahedra, corners with six OFe4 trigonal pyramids, and edges with two OFe4 trigonal pyramids. In the seventh O2- site, O2- is bonded to four Fe+2.82+ atoms to form distorted OFe4 trigonal pyramids that share corners with six OCaFe3 trigonal pyramids and edges with three OFe4 trigonal pyramids. In the eighth O2- site, O2- is bonded in a trigonal planar geometry to three equivalent Fe+2.82+ atoms. In the ninth O2- site, O2- is bonded to four Fe+2.82+ atoms to form distorted OFe4 trigonal pyramids that share corners with three equivalent OCaFe3 tetrahedra, corners with seven OFe4 trigonal pyramids, and edges with three equivalent OFe4 trigonal pyramids.