Materials Data on CaAl2Si2(H2O5)2 by Materials Project

Abstract

CaAl2Si2(H2O5)2 crystallizes in the orthorhombic Cmcm space group. The structure is three-dimensional. Ca2+ is bonded to six O2- atoms to form distorted CaO6 octahedra that share corners with four equivalent AlO6 octahedra and corners with six equivalent SiO4 tetrahedra. The corner-sharing octahedral tilt angles are 64°. There are a spread of Ca–O bond distances ranging from 2.39–2.56 Å. Al3+ is bonded to six O2- atoms to form AlO6 octahedra that share corners with two equivalent CaO6 octahedra, corners with four equivalent SiO4 tetrahedra, and edges with two equivalent AlO6 octahedra. The corner-sharing octahedral tilt angles are 64°. There are a spread of Al–O bond distances ranging from 1.88–1.98 Å. Si4+ is bonded to four O2- atoms to form SiO4 tetrahedra that share corners with three equivalent CaO6 octahedra, corners with four equivalent AlO6 octahedra, and a cornercorner with one SiO4 tetrahedra. The corner-sharing octahedra tilt angles range from 49–69°. There are a spread of Si–O bond distances ranging from 1.64–1.67 Å. There are two inequivalent H1+ sites. In the first H1+ site, H1+ is bonded in a single-bond geometry to one O2- atom. The H–O bond length is 0.99 Å. In the second H1+ site, H1+ is bonded in a single-bond geometry to one O2- atom. The H–O bond length is 0.98 Å. There are five inequivalent O2- sites. In the first O2- site, O2- is bonded in a 3-coordinate geometry to one Ca2+ and two equivalent Si4+ atoms. In the second O2- site, O2- is bonded in a distorted trigonal planar geometry to one Ca2+, one Al3+, and one Si4+ atom. In the third O2- site, O2- is bonded in a 3-coordinate geometry to two equivalent Al3+ and one Si4+ atom. In the fourth O2- site, O2- is bonded in a distorted single-bond geometry to two equivalent Al3+ and one H1+ atom. In the fifth O2- site, O2- is bonded in a distorted bent 120 degrees geometry to one Ca2+ and two equivalent H1+ atoms.