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

Single crystals of five compounds with approximate compositions ∼Ru(16)(Al(0.78)Si(0.22))(47), (I), ∼Ru(9)(Al(0.70)Si(0.30))(32), (II), ∼Ru(10)(Al(0.67)Si(0.33))(41), (III), ∼Ru(Al(0.57)Si(0.43))(5), (IV), and ∼Ru(2)(Al(0.46)Si(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 ∼Fe(9)(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 LiIrSn(4) type. The crystal structure of (V) can be viewed as a crystallographic shear structure derived from that of (IV).