Study of Al-Cu Hume-Rothery alloys and their relationship to the electronic properties of quasicrystals

• Published in: Journal of physics. Condensed matter Vol. 10; no. 19; pp. 4231 - 4244
• Main Authors: Fournée, Vincent, Belin-Ferré, Esther, Dubois, Jean-Marie
• Format: Journal Article
• Language: English
• Published: Bristol IOP Publishing 18.05.1998; Institute of Physics
• Subjects: Applied sciences; Condensed matter: electronic structure, electrical, magnetic, and optical properties; Electron states; Electronic structure of disordered solids; Exact sciences and technology; Metals. Metallurgy; Physics; Quasicrystals; Fano effect; Experimental study; Quasicrystals; Hume Rothery phases; APW calculations; Binary alloys; Aluminium alloys; X-ray absorption spectra; Tight binding approximation; Copper alloys; LMTO ASA method; X-ray emission spectra; Energy-level density; Transition element alloys
• ISSN: 0953-8984; 1361-648X
• DOI: 10.1088/0953-8984/10/19/011

The stability of quasicrystals is related to the Hume-Rothery mechanism known to take place in many intermetallics, especially Al-Cu alloys. In order to assess to what extent the electronic density of states in aperiodic Al-Cu-Fe compounds is sensitive to Hume-Rothery stabilization, we present experimental measurements by soft x-ray emission and absorption spectroscopies of the aluminium electronic states in a series of Al-Cu crystalline compounds. Some of them, like icosahedral Al-Cu-Fe, are characterized by nearly spherical Brillouin zones. We observe the opening of a narrow but definite pseudo-gap in such Al-Cu compounds. We point out a strong interaction between Cu d states and the Al states in the middle of the valence band which is well described by a Fano-like effect. Some other characteristic features of our spectra are interpreted on the basis of band structure calculations. A comparison to previous data published for quasicrystalline and approximant phases stresses the importance for the stability of these compounds of sp-d hybridization at the Fermi level. It also leads to the conclusion that the effect of Hume-Rothery interaction is dramatically enhanced by the hierarchical structure of quasicrystals rather than by the almost spherical shape of the Brillouin zone.