Materials Data on CaAl2(SiO5)2 by Materials Project

Abstract

CaAl2(SiO5)2 crystallizes in the orthorhombic Cmcm space group. The structure is three-dimensional. Ca is bonded to six O 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 63°. There are a spread of Ca–O bond distances ranging from 2.38–2.51 Å. Al is bonded to six O 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 63°. There are a spread of Al–O bond distances ranging from 1.88–1.96 Å. Si is bonded to four O 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 49–68°. There are a spread of Si–O bond distances ranging from 1.63–1.66 Å. There are five 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 single-bond geometry to one Ca atom. In the third O site, O is bonded in a distorted trigonal planar geometry to one Ca and two equivalent Si atoms. In the fourth O site, O is bonded in a trigonal planar geometry to one Ca, one Al, and one Si atom. In the fifth O site, O is bonded in a 3-coordinate geometry to two equivalent Al and one Si atom.