Materials Data on CaAl12Si4O27 by Materials Project

Abstract

CaAl12Si4O27 crystallizes in the trigonal P-3 space group. The structure is three-dimensional. Ca2+ is bonded to twelve O2- atoms to form CaO12 cuboctahedra that share corners with six equivalent AlO6 octahedra, corners with six equivalent SiO6 octahedra, edges with six equivalent AlO6 octahedra, and faces with six equivalent AlO6 octahedra. The corner-sharing octahedra tilt angles range from 49–50°. There are six shorter (2.58 Å) and six longer (2.94 Å) Ca–O bond lengths. There are two inequivalent Al3+ sites. In the first Al3+ site, Al3+ is bonded to six O2- atoms to form AlO6 octahedra that share a cornercorner with one SiO6 octahedra, corners with four AlO6 octahedra, corners with two equivalent SiO4 tetrahedra, an edgeedge with one CaO12 cuboctahedra, and edges with four equivalent AlO6 octahedra. The corner-sharing octahedra tilt angles range from 0–57°. There are a spread of Al–O bond distances ranging from 1.85–2.15 Å. In the second Al3+ site, Al3+ is bonded to six O2- atoms to form AlO6 octahedra that share a cornercorner with one CaO12 cuboctahedra, corners with five AlO6 octahedra, a cornercorner with one SiO4 tetrahedra, edges with two equivalent SiO6 octahedra, edges with three equivalent AlO6 octahedra, and a faceface with one CaO12 cuboctahedra. The corner-sharing octahedra tilt angles range from 18–57°. There are a spread of Al–O bond distances ranging from 1.80–1.99 Å. There are two inequivalent Si4+ sites. In the first Si4+ site, Si4+ is bonded to four O2- atoms to form SiO4 tetrahedra that share corners with nine AlO6 octahedra. The corner-sharing octahedra tilt angles range from 54–60°. There is three shorter (1.64 Å) and one longer (1.71 Å) Si–O bond length. In the second Si4+ site, Si4+ is bonded to six O2- atoms to form SiO6 octahedra that share corners with three equivalent CaO12 cuboctahedra, corners with three equivalent AlO6 octahedra, and edges with six equivalent AlO6 octahedra. The corner-sharing octahedral tilt angles are 51°. There is three shorter (1.74 Å) and three longer (1.88 Å) Si–O bond length. There are six inequivalent O2- sites. In the first O2- site, O2- is bonded in a distorted tetrahedral geometry to three equivalent Al3+ and one Si4+ atom. In the second O2- site, O2- is bonded in an octahedral geometry to six equivalent Al3+ atoms. In the third O2- site, O2- is bonded in a distorted rectangular see-saw-like geometry to one Ca2+, three equivalent Al3+, and one Si4+ atom. In the fourth O2- site, O2- is bonded in a distorted trigonal planar geometry to two Al3+ and one Si4+ atom. In the fifth O2- site, O2- is bonded in a distorted trigonal planar geometry to two equivalent Al3+ and one Si4+ atom. In the sixth O2- site, O2- is bonded in a 3-coordinate geometry to one Ca2+ and three Al3+ atoms.