Materials Data on Ca(AlSi)2 by Materials Project

Abstract

CaAl2Si2 crystallizes in the trigonal P-3m1 space group. The structure is three-dimensional. Ca2+ is bonded to six equivalent Si4- atoms to form CaSi6 octahedra that share corners with twelve equivalent AlSi4 tetrahedra, edges with six equivalent CaSi6 octahedra, and edges with six equivalent AlSi4 tetrahedra. All Ca–Si bond lengths are 3.04 Å. Al3+ is bonded to four equivalent Si4- atoms to form AlSi4 tetrahedra that share corners with six equivalent CaSi6 octahedra, corners with six equivalent AlSi4 tetrahedra, edges with three equivalent CaSi6 octahedra, and edges with three equivalent AlSi4 tetrahedra. The corner-sharing octahedra tilt angles range from 21–52°. There are three shorter (2.52 Å) and one longer (2.60 Å) Al–Si bond lengths. Si4- is bonded to three equivalent Ca2+ and four equivalent Al3+ atoms to form a mixture of distorted edge and corner-sharing SiCa3Al4 pentagonal bipyramids.