Materials Data on KFe4(SiO4)3 by Materials Project
KFe4(SiO4)3 is Esseneite-like structured and crystallizes in the triclinic P1 space group. The structure is two-dimensional and consists of one KFe4(SiO4)3 sheet oriented in the (0, 0, 1) direction. K1+ is bonded in a 3-coordinate geometry to three O2- atoms. There are two shorter (2.66 Å) and one longer (2.67 Å) K–O bond lengths. There are four inequivalent Fe+2.75+ sites. In the first Fe+2.75+ site, Fe+2.75+ is bonded to six O2- atoms to form FeO6 octahedra that share a cornercorner with one FeO4 tetrahedra, corners with three SiO4 tetrahedra, and edges with six FeO6 octahedra. There are a spread of Fe–O bond distances ranging from 2.04–2.31 Å. In the second Fe+2.75+ site, Fe+2.75+ is bonded to six O2- atoms to form FeO6 octahedra that share a cornercorner with one FeO4 tetrahedra, corners with three SiO4 tetrahedra, and edges with six FeO6 octahedra. There are a spread of Fe–O bond distances ranging from 1.94–2.21 Å. In the third Fe+2.75+ site, Fe+2.75+ is bonded to six O2- atoms to form FeO6 octahedra that share a cornercorner with one FeO4 tetrahedra, corners with three SiO4 tetrahedra, and edges with six FeO6 octahedra. There are a spread of Fe–O bond distances ranging from 1.94–2.20 Å. In the fourth Fe+2.75+ site, Fe+2.75+ is bonded to four O2- atoms to form FeO4 tetrahedra that share corners with three FeO6 octahedra and corners with three equivalent SiO4 tetrahedra. The corner-sharing octahedra tilt angles range from 59–69°. There is three shorter (1.86 Å) and one longer (1.91 Å) Fe–O bond length. There are three 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 equivalent FeO4 tetrahedra. The corner-sharing octahedra tilt angles range from 55–60°. There are a spread of Si–O bond distances ranging from 1.62–1.70 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 three equivalent SiO4 tetrahedra. The corner-sharing octahedra tilt angles range from 54–60°. There are a spread of Si–O bond distances ranging from 1.63–1.67 Å. In the third Si4+ site, Si4+ is bonded to four O2- atoms to form SiO4 tetrahedra that share corners with three FeO6 octahedra and corners with three equivalent SiO4 tetrahedra. The corner-sharing octahedra tilt angles range from 54–62°. There is one shorter (1.63 Å) and three longer (1.66 Å) Si–O bond length. There are twelve inequivalent O2- sites. In the first O2- site, O2- is bonded in a distorted trigonal planar geometry to one K1+, one Fe+2.75+, and one Si4+ atom. In the second O2- site, O2- is bonded in a bent 150 degrees geometry to two Si4+ atoms. In the third O2- site, O2- is bonded in a distorted trigonal planar geometry to one K1+, one Fe+2.75+, and one Si4+ atom. In the fourth O2- site, O2- is bonded in a distorted trigonal planar geometry to one K1+, one Fe+2.75+, and one Si4+ atom. In the fifth O2- site, O2- is bonded in a distorted bent 150 degrees geometry to two Si4+ atoms. In the sixth O2- site, O2- is bonded in a distorted bent 150 degrees geometry to two Si4+ atoms. In the seventh O2- site, O2- is bonded in a distorted trigonal non-coplanar geometry to three Fe+2.75+ atoms. In the eighth O2- site, O2- is bonded in a distorted T-shaped geometry to three Fe+2.75+ atoms. In the ninth O2- site, O2- is bonded in a distorted tetrahedral geometry to four Fe+2.75+ atoms. In the tenth O2- site, O2- is bonded in a distorted rectangular see-saw-like geometry to three Fe+2.75+ and one Si4+ atom. In the eleventh O2- site, O2- is bonded in a distorted rectangular see-saw-like geometry to three Fe+2.75+ and one Si4+ atom. In the twelfth O2- site, O2- is bonded in a distorted rectangular see-saw-like geometry to three Fe+2.75+ and one Si4+ atom.