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

Abstract

Single crystals of five compounds with approximate compositions ∼Ru16(Al0.78Si0.22)47, (I), ∼Ru9(Al0.70Si0.30)32, (II), ∼Ru10(Al0.67Si0.33)41, (III), ∼Ru(Al0.57Si0.43)5, (IV), and ∼Ru2(Al0.46Si0.54)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 icosahedral 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).

Keywords

• crystal structure
• aluminium–ruthenium–silicon system
• single-crystal x-ray diffraction
• isotypism
• structural similarity
• crystallographic shear
• unit-cell twinning
• quasicrystal approximant