Crystal structures of the compounds GdAl0.09Ge2.07 and Gd2AlGe3

Abstract

Two gadolinium alumogermanides, GdAl 0.09(3) Ge 2.07(4) and Gd 2 AlGe 3 , were synthesized by arc melting and their crystal structures were studied by X-ray powder diffraction. The compound GdAl 0.09 Ge 2.07 crystallizes with an ErGe 2.16-type structure: Pearson symbol oS16, space group Cmcm, a = 4.1704(5), b = 16.447(2), c = 3.9820(5) Å. It is the second known representative of the structure type ErGe 2.16 (a binary variant of the type CeNiSi 2) among rare-earth alumogermanides; in both cases Al was found to partially substitute for Ge on one of the fully occupied Ge sites. The compound Gd 2 AlGe 3 is isostructural to Y 2 AlGe 3 : Pearson symbol oP24, space group Pnma, a = 6.8031(2), b = 4.2282(1), c = 17.8165(5) Å, and is the ninth representative of this type. Common to the two structures is the presence of layers of Ge-centered Gd 6 trigonal prisms sharing the bases and two of the three lateral faces.