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All sourcesNASA NTRSDOE OSTI
DOE OSTI2020

Materials Data on Fe7(SiO4)4 by Materials Project

Fe7(SiO4)4 crystallizes in the monoclinic P2_1/c space group. The structure is three-dimensional. there are four inequivalent Fe+2.29+ sites. In the first Fe+2.29+ site, Fe+2.29+ is bonded to six O2- atoms to form FeO6 octahedra that share corners with four equivalent FeO6 octahedra, corners with two equivalent SiO4 tetrahedra, edges with four FeO6 octahedra, and edges with two equivalent SiO4 tetrahedra. The corner-sharing octahedra tilt angles range from 57–66°. There are a spread of Fe–O bond distances ranging from 2.16–2.25 Å. In the second Fe+2.29+ site, Fe+2.29+ is bonded to six O2- atoms to form FeO6 octahedra that share corners with four FeO6 octahedra, corners with two SiO4 tetrahedra, edges with three FeO6 octahedra, and edges with two SiO4 tetrahedra. The corner-sharing octahedra tilt angles range from 56–66°. There are a spread of Fe–O bond distances ranging from 2.09–2.25 Å. In the third Fe+2.29+ site, Fe+2.29+ is bonded to six O2- atoms to form FeO6 octahedra that share corners with eight FeO6 octahedra, corners with four SiO4 tetrahedra, edges with two FeO6 octahedra, and an edgeedge with one SiO4 tetrahedra. The corner-sharing octahedra tilt angles range from 47–66°. There are a spread of Fe–O bond distances ranging from 2.12–2.33 Å. In the fourth Fe+2.29+ site, Fe+2.29+ is bonded to six O2- atoms to form FeO6 octahedra that share corners with six FeO6 octahedra, corners with four SiO4 tetrahedra, an edgeedge with one FeO6 octahedra, and an edgeedge with one SiO4 tetrahedra. The corner-sharing octahedra tilt angles range from 47–66°. There are a spread of Fe–O bond distances ranging from 1.99–2.15 Å. 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 six FeO6 octahedra and edges with three FeO6 octahedra. The corner-sharing octahedra tilt angles range from 53–62°. There are a spread of Si–O bond distances ranging from 1.64–1.67 Å. In the second Si4+ site, Si4+ is bonded to four O2- atoms to form SiO4 tetrahedra that share corners with five FeO6 octahedra and edges with two FeO6 octahedra. The corner-sharing octahedra tilt angles range from 45–60°. There are a spread of Si–O bond distances ranging from 1.62–1.68 Å. There are eight inequivalent O2- sites. In the first O2- site, O2- is bonded in a 4-coordinate geometry to three Fe+2.29+ and one Si4+ atom. In the second O2- site, O2- is bonded in a distorted trigonal planar geometry to two equivalent Fe+2.29+ and one Si4+ atom. In the third O2- site, O2- is bonded in a distorted rectangular see-saw-like geometry to three Fe+2.29+ and one Si4+ atom. In the fourth O2- site, O2- is bonded in a distorted rectangular see-saw-like geometry to three Fe+2.29+ and one Si4+ atom. In the fifth O2- site, O2- is bonded in a distorted rectangular see-saw-like geometry to three Fe+2.29+ and one Si4+ atom. In the sixth O2- site, O2- is bonded in a 4-coordinate geometry to three Fe+2.29+ and one Si4+ atom. In the seventh O2- site, O2- is bonded in a distorted trigonal planar geometry to two Fe+2.29+ and one Si4+ atom. In the eighth O2- site, O2- is bonded in a 3-coordinate geometry to two Fe+2.29+ and one Si4+ atom.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Fe7(SiO3)8 by Materials Project

Fe7(SiO3)8 crystallizes in the monoclinic C2/m space group. The structure is three-dimensional. there are four inequivalent Fe+2.29+ sites. In the first Fe+2.29+ site, Fe+2.29+ is bonded in a distorted rectangular see-saw-like geometry to four O2- atoms. There are two shorter (2.03 Å) and two longer (2.17 Å) Fe–O bond lengths. In the second Fe+2.29+ site, Fe+2.29+ is bonded to six O2- atoms to form FeO6 octahedra that share corners with six SiO4 tetrahedra and edges with three FeO6 octahedra. There are a spread of Fe–O bond distances ranging from 2.09–2.22 Å. In the third Fe+2.29+ site, Fe+2.29+ is bonded to six O2- atoms to form FeO6 octahedra that share corners with four equivalent SiO4 tetrahedra and edges with six FeO6 octahedra. There are two shorter (1.95 Å) and four longer (2.11 Å) Fe–O bond lengths. In the fourth Fe+2.29+ site, Fe+2.29+ is bonded to six O2- atoms to form FeO6 octahedra that share corners with four SiO4 tetrahedra and edges with five FeO6 octahedra. There are a spread of Fe–O bond distances ranging from 2.01–2.22 Å. 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 three SiO4 tetrahedra. The corner-sharing octahedra tilt angles range from 59–60°. There are a spread of Si–O bond distances ranging from 1.62–1.65 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 38–60°. There are a spread of Si–O bond distances ranging from 1.63–1.66 Å. There are seven inequivalent O2- sites. In the first O2- site, O2- is bonded in a bent 150 degrees geometry to two equivalent Si4+ atoms. In the second O2- site, O2- is bonded in a distorted trigonal non-coplanar geometry to three Fe+2.29+ atoms. In the third O2- site, O2- is bonded in a bent 150 degrees geometry to two Si4+ atoms. In the fourth O2- site, O2- is bonded in a distorted trigonal non-coplanar geometry to two Fe+2.29+ and one Si4+ atom. In the fifth O2- site, O2- is bonded in a 4-coordinate geometry to three Fe+2.29+ and one Si4+ atom. In the sixth O2- site, O2- is bonded in a distorted rectangular see-saw-like geometry to three Fe+2.29+ and one Si4+ atom. In the seventh O2- site, O2- is bonded in a distorted bent 150 degrees geometry to two Si4+ atoms.

36 MATERIALS SCIENCE↗