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A first principle study of lead adsorption on the pseudo-10-fold surface of the orthorhombic Al13Co4 intermetallic compound has been performed using four possible structural models as substrate. Coverage between atomic adsorption to near 0.08 atm./Å2 has been considered. Relative adsorption energies of Pb atoms on different surface sites in addition with simulated scanning tunneling microscopy images were obtained for each model. Our ab initio calculations demonstrate that the experimental results published recently, highlighting (i) the presence of a preferential adsorption site and (ii) the formation of Pb rows extending along the [010] direction [ N. J. Phys. 2011, 13, 10301114] can be only reproduced using a dense Al-rich termination as the substrate structural model. This result confirms the previously established structural model for the (100) surface of orthorhombic Al13Co4 [ Phys. Rev. B 2011, 84, 085411]. This study then provides an understanding of the experimental observations for the different lead coverages. © 2012 Wiley Periodicals, Inc. [ABSTRACT FROM AUTHOR]

We have investigated the adsorption of Pb atoms on the (100) surface of an orthorhombic Al13Co4 crystal at 300 and 573K substrate temperatures. This complex metallic alloy is an approximant to the decagonal Al-Ni-Co quasicrystal. At submonolayer coverage and at 300 K, Pb adatoms remain highly mobile and adsorb preferentially within the hollow site situated in between adjacent Al pentagonal clusters present at the surface. These experimental findings are supported by ab initio calculations based on density functional theory (DFT). For both temperature regimes, Pb adsorption leads to the formation of pseudomorphic monolayers above which the high adsorbate mobility prohibits the growth of additional layers. For the high-temperature deposition, we propose a structural model for the Pb film and discuss its relationship with the underneath substrate. [ABSTRACT FROM AUTHOR]

The structure of the valence bands in a number of complex alloys was investigated using X-ray emission spectroscopy, focusing on the distribution of d-like states in a series of Al- and Mg-based alloys. A substantial density of d-like states was found at or just under the Fermi level in the Al s,d and Mg s,d distributions of these complex systems. It is suggested that d-like states play a significant role in local symmetry of the crystals and contribute to selecting and stabilizing their structures. [ABSTRACT FROM AUTHOR]

Although the industrial development of complex metallic alloys (CMAs) and quasicrystals (QCs) has remained quite limited so far, these materials exhibit interesting and sometimes unexpected properties in terms of technological applications. A few selected examples of the most promising properties and trends for potential applications are presented. [ABSTRACT FROM AUTHOR]

Pseudo-binary IQC 100- x DQC x alloys made from mixing Al 62 Cu 25.5 Fe 12.5 icosahedral quasicrystal (IQC) and Al 70 Co 15 Ni 15 decagonal quasicrystal (DQC) together in progressively increased proportions were studied by X-ray diffraction (XRD), scanning electron microscopy (SEM) and energy-dispersive X-ray spectroscopy (EDAX). In this way the transition from IQC to DQC was manifested by the evolution of their constituent phases. The formation of these phases was found to follow the evolution of their valence electron concentration per atom ( e/a ) lines in the Al–(Cu,Ni)–(Fe,Co) pseudo-ternary phase diagram. An Al–Cu–Co type decagonal phase was found in the annealed IQC 80 DQC 20 alloy. This phase is characterized by transmission electron microscopy (TEM) and by high-resolution electron microscopy (HREM). The study proved that it is a superstructure of the DQC phase. The possible origin of its formation was discussed according to the variation of its DQC formation e/a -constant line in the Al–(Cu,Ni)–(Fe,Co) alloy system. [ABSTRACT FROM AUTHOR]

We have characterized by transmission electron microscopy several new phases that we have discovered in bulk alloys of the Al–Cr–Fe system. These structures are an icosahedral compound and several approximants of the decagonal phase. According to the indexation of the electron diffraction patterns (EDPs), some of the approximants are not of Fibonacci type. These EDPs correspond to nanodomains, which are due to disorder introduced by quenching the alloys after melting the pure constituent metals. For these new types of approximant, we propose a crystallographic description related to the usual Fibonacci description. In addition, we suggest a construction of the corresponding tilings. The orientation relationships between these structures are described. [ABSTRACT FROM AUTHOR]