Materials Data on KAl4Fe3(HO6)2 by Materials Project
KFe3Al4(HO6)2 crystallizes in the monoclinic C2/m space group. The structure is three-dimensional. K1+ is bonded to six O2- atoms to form distorted KO6 octahedra that share corners with twelve equivalent AlO4 tetrahedra. All K–O bond lengths are 2.80 Å. There are two inequivalent Fe3+ sites. In the first Fe3+ site, Fe3+ is bonded to six O2- atoms to form FeO6 octahedra that share corners with four equivalent AlO4 tetrahedra and edges with six equivalent FeO6 octahedra. There are four shorter (2.06 Å) and two longer (2.11 Å) Fe–O bond lengths. In the second Fe3+ site, Fe3+ is bonded to six O2- atoms to form FeO6 octahedra that share corners with four equivalent AlO4 tetrahedra and edges with six FeO6 octahedra. There are a spread of Fe–O bond distances ranging from 2.03–2.11 Å. Al3+ is bonded to four O2- atoms to form AlO4 tetrahedra that share corners with three equivalent KO6 octahedra, corners with three FeO6 octahedra, and corners with three equivalent AlO4 tetrahedra. The corner-sharing octahedra tilt angles range from 61–66°. There is three shorter (1.74 Å) and one longer (1.92 Å) Al–O bond length. H1+ is bonded in a single-bond geometry to one O2- atom. The H–O bond length is 0.99 Å. There are four inequivalent O2- sites. In the first O2- site, O2- is bonded to three Fe3+ and one Al3+ atom to form a mixture of distorted edge and corner-sharing OAlFe3 tetrahedra. In the second O2- site, O2- is bonded in a distorted single-bond geometry to three Fe3+ and one H1+ atom. In the third O2- site, O2- is bonded in a distorted trigonal planar geometry to one K1+ and two equivalent Al3+ atoms. In the fourth O2- site, O2- is bonded in a distorted trigonal planar geometry to one K1+ and two equivalent Al3+ atoms.