Materials Data on Mg(AlGe)2 by Materials Project
MgAl2Ge2 crystallizes in the trigonal P-3m1 space group. The structure is three-dimensional. Mg is bonded to six equivalent Ge atoms to form MgGe6 octahedra that share corners with twelve equivalent AlGe4 tetrahedra, edges with six equivalent MgGe6 octahedra, and edges with six equivalent AlGe4 tetrahedra. All Mg–Ge bond lengths are 2.90 Å. Al is bonded to four equivalent Ge atoms to form AlGe4 tetrahedra that share corners with six equivalent MgGe6 octahedra, corners with six equivalent AlGe4 tetrahedra, edges with three equivalent MgGe6 octahedra, and edges with three equivalent AlGe4 tetrahedra. The corner-sharing octahedra tilt angles range from 15–55°. There are three shorter (2.53 Å) and one longer (2.65 Å) Al–Ge bond lengths. Ge is bonded to three equivalent Mg and four equivalent Al atoms to form a mixture of distorted edge and corner-sharing GeMg3Al4 pentagonal bipyramids.