Materials Data on CaAl2Si2HO9 by Materials Project
(CaAl2Si2O9)2H2 crystallizes in the orthorhombic Cmcm space group. The structure is three-dimensional and consists of four hydrogen molecules and one CaAl2Si2O9 framework. In the CaAl2Si2O9 framework, Ca is bonded in a 5-coordinate geometry to five O atoms. There are four shorter (2.39 Å) and one longer (2.50 Å) Ca–O bond lengths. Al is bonded to six O atoms to form AlO6 octahedra that share corners with four equivalent SiO4 tetrahedra and edges with two equivalent AlO6 octahedra. There are a spread of Al–O bond distances ranging from 1.88–1.97 Å. Si is bonded to four O atoms to form SiO4 tetrahedra that share corners with four equivalent AlO6 octahedra and a cornercorner with one SiO4 tetrahedra. The corner-sharing octahedra tilt angles range from 48–62°. There are a spread of Si–O bond distances ranging from 1.64–1.67 Å. There are four inequivalent O sites. In the first O site, O is bonded in a water-like geometry to two equivalent Al atoms. In the second O site, O is bonded in a distorted trigonal planar geometry to one Ca and two equivalent Si atoms. In the third O site, O is bonded in a 3-coordinate geometry to two equivalent Al and one Si atom. In the fourth O site, O is bonded in a trigonal planar geometry to one Ca, one Al, and one Si atom.