Materials Data on CaFe3Si2HO9 by Materials Project

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.

CaFe₃Si₂HO₉结晶于单斜晶系P2₁/c（monoclinic P2₁/c）空间群。该晶体为三维网状结构。Ca²+与7个O²-配位，形成畸变的CaO₇五角双锥（distorted CaO₇ pentagonal bipyramid），该五角双锥与5个SiO₄四面体（SiO₄ tetrahedron）共角、与6个FeO₆八面体（FeO₆ octahedron）共边，还与1个SiO₄四面体形成边-边连接。Ca—O键的键长分布范围为2.32~2.49 Å。
存在3个不等价的Fe².33+配位位点。在第一个Fe².33+位点中，Fe².33+与6个O²-配位，形成FeO₆八面体，该八面体与2个等价的FeO₆八面体共角、与3个SiO₄四面体共角、与5个FeO₆八面体共边，还与2个等价的CaO₇五角双锥共边。其共角八面体倾斜角为17°。Fe—O键的键长分布范围为2.06~2.30 Å。
在第二个Fe².33+位点中，Fe².33+与6个O²-配位，形成FeO₆八面体，该八面体与2个等价的FeO₆八面体共角、与3个SiO₄四面体共角、与5个FeO₆八面体共边，还与2个等价的CaO₇五角双锥共边。其共角八面体倾斜角为17°。Fe—O键的键长分布范围为1.97~2.11 Å。
在第三个Fe².33+位点中，Fe².33+与6个O²-配位，形成FeO₆八面体，该八面体与5个SiO₄四面体共角、与4个FeO₆八面体共边，还与2个等价的CaO₇五角双锥共边。Fe—O键的键长分布范围为1.99~2.34 Å。
存在2个不等价的Si⁴+配位位点。在第一个Si⁴+位点中，Si⁴+与4个O²-配位，形成SiO₄四面体，该四面体与5个FeO₆八面体共角、与3个等价的CaO₇五角双锥共角，还与1个SiO₄四面体形成角-角连接。其共角八面体倾斜角范围为47°~62°。Si—O键的键长分布范围为1.62~1.67 Å。
在第二个Si⁴+位点中，Si⁴+与4个O²-配位，形成SiO₄四面体，该四面体与6个FeO₆八面体共角、与2个等价的CaO₇五角双锥共角、与1个SiO₄四面体形成角-角连接，还与1个CaO₇五角双锥形成边-边连接。其共角八面体倾斜角范围为45°~65°。Si—O键的键长分布范围为1.65~1.68 Å。
H⁺以畸变单键配位几何与2个O²-配位，存在1个较短的H—O键长（1.00 Å）和1个较长的H—O键长（1.65 Å）。
存在9个不等价的O²-配位位点。
在第一个O²-位点中，O²-以畸变的矩形跷跷板型配位几何与1个Ca²+、2个Fe².33+和1个Si⁴+原子配位。
在第二个O²-位点中，O²-以畸变的矩形跷跷板型配位几何与1个Ca²+、2个Fe².33+和1个Si⁴+原子配位。
在第三个O²-位点中，O²-以畸变的矩形跷跷板型配位几何与1个Ca²+、2个Fe².33+和1个Si⁴+原子配位。
在第四个O²-位点中，O²-以畸变的矩形跷跷板型配位几何与1个Ca²+、2个Fe².33+和1个Si⁴+原子配位。
在第五个O²-位点中，O²-以畸变单键几何与1个Ca²+、2个Fe².33+和1个H⁺原子配位。
在第六个O²-位点中，O²-以畸变的矩形跷跷板型配位几何与1个Ca²+、2个Fe².33+和1个Si⁴+原子配位。
在第七个O²-位点中，O²-以三配位几何与1个Ca²+和2个Si⁴+原子配位。
在第八个O²-位点中，O²-以三配位几何与1个Fe².33+、1个Si⁴+和1个H⁺原子配位。
在第九个O²-位点中，O²-与5个Fe².33+原子配位，形成共边连接的OFe₅四方锥（OFe₅ square pyramid）。