Crystal structures of five compounds in the aluminium-ruthenium-silicon system.

Single crystals of five compounds with approximate compositions ∼Ru(AlSi), (I), ∼Ru(AlSi), (II), ∼Ru(AlSi), (III), ∼Ru(AlSi), (IV), and ∼Ru(AlSi), (V), were obtained from polycrystalline lumps mainly composed of the target compounds, and their crystal structures were determined by means of single-crystal X-ray diffraction. The crystal structure of (I) can be related to that of a cubic rational crystalline approximant to an icosa-hedral quasicrystal through crystallographic shear and then unit-cell twinning. The crystal structure of (II) is isotypic with that of a phase with composition ∼Fe(Al,Si). The crystal structure of (III) is comprised of edge-sharing Ru(Al,Si) polyhedra with disordered chains along edges of polyhedra. The crystal structure of (IV) is of the LiIrSn type. The crystal structure of (V) can be viewed as a crystallographic shear structure derived from that of (IV).