Crystal structure re-determination of binary IrAl2.75 into Ir8Al21.22

Abstract

The Ir₈Al_21.22 binary intermetallic compound was synthesized using arc melting technique. Its crystal structure probed by single-crystal X-ray diffraction is a superstructure variant of the previously reported cubic IrAl_2.75 compound. Ir₈Al_21.22 crystallizes in the Fmm2 space group with the unit cell parameters of a = 15.3307(9) Å, b = 15.3226(10) Å, c = 15.3129(9) Å, and V = 3597.1(4) ų. The crystal structure contains columns of interpenetrating distorted icosahedral clusters – a characteristic feature of the approximant phases and quasicrystals. Electronic structure calculations indicate strong hybridization between valence orbitals of iridium and aluminum atoms accompanied by the formation of pseudogap, which separates the valence and conduction bands.