Materials Data on Ca(AlGe)2 by Materials Project

Abstract

CaAl2Ge2 crystallizes in the trigonal P-3m1 space group. The structure is three-dimensional. Ca is bonded to six equivalent Ge atoms to form CaGe6 octahedra that share corners with twelve equivalent AlGe4 tetrahedra, edges with six equivalent CaGe6 octahedra, and edges with six equivalent AlGe4 tetrahedra. All Ca–Ge bond lengths are 3.06 Å. Al is bonded to four equivalent Ge atoms to form AlGe4 tetrahedra that share corners with six equivalent CaGe6 octahedra, corners with six equivalent AlGe4 tetrahedra, edges with three equivalent CaGe6 octahedra, and edges with three equivalent AlGe4 tetrahedra. The corner-sharing octahedra tilt angles range from 19–53°. There are three shorter (2.56 Å) and one longer (2.65 Å) Al–Ge bond lengths. Ge is bonded to three equivalent Ca and four equivalent Al atoms to form a mixture of distorted edge and corner-sharing GeCa3Al4 pentagonal bipyramids.