DOI: 10.17188/1287417
title: Materials Data on CaFe3Si2HO9 by Materials Project

description: CaFe3Si2HO9 crystallizes in the monoclinic P2_1/c space group. The structure is three-dimensional. Ca2+ is bonded to seven O2- atoms to form distorted CaO7 pentagonal bipyramids that share corners with five SiO4 tetrahedra, edges with six FeO6 octahedra, and an edgeedge with one SiO4 tetrahedra. There are a spread of Ca–O bond distances ranging from 2.32–2.49 Å. There are three inequivalent Fe+2.33+ sites. In the first Fe+2.33+ site, Fe+2.33+ is bonded to six O2- atoms to form FeO6 octahedra that share corners with two equivalent FeO6 octahedra, corners with three SiO4 tetrahedra, edges with five FeO6 octahedra, and edges with two equivalent CaO7 pentagonal bipyramids. The corner-sharing octahedral tilt angles are 17°. There are a spread of Fe–O bond distances ranging from 2.06–2.30 Å. In the second Fe+2.33+ site, Fe+2.33+ is bonded to six O2- atoms to form FeO6 octahedra that share corners with two equivalent FeO6 octahedra, corners with three SiO4 tetrahedra, edges with five FeO6 octahedra, and edges with two equivalent CaO7 pentagonal bipyramids. The corner-sharing octahedral tilt angles are 17°. There are a spread of Fe–O bond distances ranging from 1.97–2.11 Å. In the third Fe+2.33+ site, Fe+2.33+ is bonded to six O2- atoms to form FeO6 octahedra that share corners with five SiO4 tetrahedra, edges with four FeO6 octahedra, and edges with two equivalent CaO7 pentagonal bipyramids. There are a spread of Fe–O bond distances ranging from 1.99–2.34 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 five FeO6 octahedra, corners with three equivalent CaO7 pentagonal bipyramids, and a cornercorner with one SiO4 tetrahedra. The corner-sharing octahedra tilt angles range from 47–62°. There are a spread of Si–O bond distances ranging from 1.62–1.67 Å. In the second Si4+ site, Si4+ is bonded to four O2- atoms to form SiO4 tetrahedra that share corners with six FeO6 octahedra, corners with two equivalent CaO7 pentagonal bipyramids, a cornercorner with one SiO4 tetrahedra, and an edgeedge with one CaO7 pentagonal bipyramid. The corner-sharing octahedra tilt angles range from 45–65°. There are a spread of Si–O bond distances ranging from 1.65–1.68 Å. H1+ is bonded in a distorted single-bond geometry to two O2- atoms. There is one shorter (1.00 Å) and one longer (1.65 Å) H–O bond length. There are nine inequivalent O2- sites. In the first O2- site, O2- is bonded in a distorted rectangular see-saw-like geometry to one Ca2+, two Fe+2.33+, and one Si4+ atom. In the second O2- site, O2- is bonded in a distorted rectangular see-saw-like geometry to one Ca2+, two Fe+2.33+, and one Si4+ atom. In the third O2- site, O2- is bonded in a distorted rectangular see-saw-like geometry to one Ca2+, two Fe+2.33+, and one Si4+ atom. In the fourth O2- site, O2- is bonded in a distorted rectangular see-saw-like geometry to one Ca2+, two Fe+2.33+, and one Si4+ atom. In the fifth O2- site, O2- is bonded in a distorted single-bond geometry to one Ca2+, two Fe+2.33+, and one H1+ atom. In the sixth O2- site, O2- is bonded in a distorted rectangular see-saw-like geometry to one Ca2+, two Fe+2.33+, and one Si4+ atom. In the seventh O2- site, O2- is bonded in a 3-coordinate geometry to one Ca2+ and two Si4+ atoms. In the eighth O2- site, O2- is bonded in a 3-coordinate geometry to one Fe+2.33+, one Si4+, and one H1+ atom. In the ninth O2- site, O2- is bonded to five Fe+2.33+ atoms to form edge-sharing OFe5 square pyramids.