Materials Data on CaFeO2 by Materials Project

CaFeO2 crystallizes in the triclinic P-1 space group. The structure is three-dimensional. there are two inequivalent Ca2+ sites. In the first Ca2+ site, Ca2+ is bonded to five O2- atoms to form distorted CaO5 trigonal bipyramids that share corners with four equivalent CaO4 tetrahedra, corners with two equivalent FeO5 trigonal bipyramids, edges with two equivalent CaO5 trigonal bipyramids, and a faceface with one FeO5 trigonal bipyramid. There are a spread of Ca–O bond distances ranging from 2.28–2.42 Å. In the second Ca2+ site, Ca2+ is bonded to four O2- atoms to form CaO4 tetrahedra that share corners with two equivalent CaO4 tetrahedra, corners with four equivalent CaO5 trigonal bipyramids, corners with four equivalent FeO5 trigonal bipyramids, and an edgeedge with one FeO5 trigonal bipyramid. There are three shorter (2.23 Å) and one longer (2.31 Å) Ca–O bond lengths. There are two inequivalent Fe2+ sites. In the first Fe2+ site, Fe2+ is bonded in a rectangular see-saw-like geometry to four O2- atoms. There are a spread of Fe–O bond distances ranging from 2.00–2.21 Å. In the second Fe2+ site, Fe2+ is bonded to five O2- atoms to form distorted FeO5 trigonal bipyramids that share corners with four equivalent CaO4 tetrahedra, corners with two equivalent CaO5 trigonal bipyramids, an edgeedge with one CaO4 tetrahedra, edges with two equivalent FeO5 trigonal bipyramids, and a faceface with one CaO5 trigonal bipyramid. There are a spread of Fe–O bond distances ranging from 2.06–2.38 Å. There are four inequivalent O2- sites. In the first O2- site, O2- is bonded to one Ca2+ and three Fe2+ atoms to form distorted OCaFe3 tetrahedra that share corners with two equivalent OCaFe3 tetrahedra, corners with four equivalent OCa3Fe2 trigonal bipyramids, and an edgeedge with one OCa3Fe2 trigonal bipyramid. In the second O2- site, O2- is bonded in a rectangular see-saw-like geometry to two equivalent Ca2+ and two equivalent Fe2+ atoms. In the third O2- site, O2- is bonded to three Ca2+ and two equivalent Fe2+ atoms to form distorted OCa3Fe2 trigonal bipyramids that share corners with four equivalent OCaFe3 tetrahedra, an edgeedge with one OCaFe3 tetrahedra, and edges with two equivalent OCa3Fe2 trigonal bipyramids. In the fourth O2- site, O2- is bonded in a 5-coordinate geometry to three Ca2+ and two equivalent Fe2+ atoms.