Materials Data on CaFe3(SiO3)4 by Materials Project
CaFe3(SiO3)4 is Esseneite-like structured and crystallizes in the monoclinic C2 space group. The structure is three-dimensional. Ca2+ is bonded in a 8-coordinate geometry to eight O2- atoms. There are a spread of Ca–O bond distances ranging from 2.30–2.73 Å. There are three inequivalent Fe2+ sites. In the first Fe2+ site, Fe2+ is bonded to six O2- atoms to form FeO6 octahedra that share corners with six SiO4 tetrahedra and edges with two equivalent FeO6 octahedra. There are a spread of Fe–O bond distances ranging from 2.07–2.24 Å. In the second Fe2+ site, Fe2+ is bonded to six O2- atoms to form FeO6 octahedra that share corners with six SiO4 tetrahedra and edges with two equivalent FeO6 octahedra. There are a spread of Fe–O bond distances ranging from 2.12–2.24 Å. In the third Fe2+ site, Fe2+ is bonded in a rectangular see-saw-like geometry to four O2- atoms. There are two shorter (2.05 Å) and two longer (2.12 Å) Fe–O bond lengths. There are two inequivalent Si4+ sites. In the first Si4+ site, Si4+ is bonded to four O2- atoms to form SiO4 tetrahedra that share corners with three FeO6 octahedra and corners with two equivalent SiO4 tetrahedra. The corner-sharing octahedra tilt angles range from 38–57°. There are a spread of Si–O bond distances ranging from 1.61–1.69 Å. In the second Si4+ site, Si4+ is bonded to four O2- atoms to form SiO4 tetrahedra that share corners with three FeO6 octahedra and corners with two equivalent SiO4 tetrahedra. The corner-sharing octahedra tilt angles range from 39–60°. There are a spread of Si–O bond distances ranging from 1.63–1.68 Å. There are six inequivalent O2- sites. In the first O2- site, O2- is bonded in a 2-coordinate geometry to one Ca2+ and two Si4+ atoms. In the second O2- site, O2- is bonded in a 2-coordinate geometry to one Ca2+ and two Si4+ atoms. In the third O2- site, O2- is bonded in a 4-coordinate geometry to three Fe2+ and one Si4+ atom. In the fourth O2- site, O2- is bonded in a 4-coordinate geometry to one Ca2+, two Fe2+, and one Si4+ atom. In the fifth O2- site, O2- is bonded in a distorted T-shaped geometry to one Ca2+, one Fe2+, and one Si4+ atom. In the sixth O2- site, O2- is bonded in a 3-coordinate geometry to two Fe2+ and one Si4+ atom.