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

Single crystals of five compounds with approximate compositions ∼Ru₁₆(Al_0.78Si_0.22)₄₇, (I), ∼Ru₉(Al_0.70Si_0.30)₃₂, (II), ∼Ru₁₀(Al_0.67Si_0.33)₄₁, (III), ∼Ru(Al_0.57Si_0.43)₅, (IV), and ∼Ru₂(Al_0.46Si_0.54)₉, (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 ∼Fe₉(Al,Si)₃₂. The crystal structure of (III) is comprised of edge-sharing Ru(Al,Si)_9-11 polyhedra with disordered chains along edges of polyhedra. The crystal structure of (IV) is of the LiIrSn₄ type. The crystal structure of (V) can be viewed as a crystallographic shear structure derived from that of (IV).