Materials Data on CaAl2SiO6 by Materials Project

Abstract

CaAl2SiO6 is Esseneite-like structured and crystallizes in the monoclinic Cc space group. The structure is three-dimensional. Ca2+ is bonded in a 8-coordinate geometry to eight O2- atoms. There are a spread of Ca–O bond distances ranging from 2.37–2.73 Å. There are two inequivalent Al3+ sites. In the first Al3+ site, Al3+ is bonded to four O2- atoms to form AlO4 tetrahedra that share corners with three equivalent AlO6 octahedra and corners with two equivalent AlO4 tetrahedra. The corner-sharing octahedra tilt angles range from 41–64°. There are a spread of Al–O bond distances ranging from 1.74–1.80 Å. In the second Al3+ site, Al3+ is bonded to six O2- atoms to form AlO6 octahedra that share corners with three equivalent AlO4 tetrahedra, corners with three equivalent SiO4 tetrahedra, and edges with two equivalent AlO6 octahedra. There are a spread of Al–O bond distances ranging from 1.85–2.09 Å. Si4+ is bonded to four O2- atoms to form SiO4 tetrahedra that share corners with three equivalent AlO6 octahedra and corners with two equivalent SiO4 tetrahedra. The corner-sharing octahedra tilt angles range from 31–59°. There are a spread of Si–O bond distances ranging from 1.61–1.68 Å. There are six inequivalent O2- sites. In the first O2- site, O2- is bonded in a 4-coordinate geometry to one Ca2+ and three Al3+ atoms. In the second O2- site, O2- is bonded in a distorted T-shaped geometry to one Ca2+ and two Al3+ atoms. In the third O2- site, O2- is bonded in a 4-coordinate geometry to two equivalent Ca2+ and two equivalent Al3+ atoms. In the fourth O2- site, O2- is bonded to one Ca2+, two equivalent Al3+, and one Si4+ atom to form distorted corner-sharing OCaAl2Si tetrahedra. In the fifth O2- site, O2- is bonded in a 2-coordinate geometry to one Ca2+, one Al3+, and one Si4+ atom. In the sixth O2- site, O2- is bonded in a 2-coordinate geometry to two equivalent Ca2+ and two equivalent Si4+ atoms.