Complex intermetallic structures can be found in many intermetallic systems and exhibit giant unit cells. They feature quite a number of peculiar structural and physical properties and have, until now, barely been treated in a unifying matter. We are following an integrated approach towards their description and categorization and are thereby formulating a fundamental definition of these very interesting and rather diverse compounds.

Much attention has been given to bulk metallic glasses (BMG) in recent years, particularly those based on binary alloys due to the simplicity of their atomic composition. Although efforts to understand the atomistic features that give rise to their exceptional properties have been made, the electronic and vibrational properties have been disregarded. We undertook the task of simulating the Cu64Zr36 glassy metal using a supercell with 108 atoms and a different simulational approach: the undermelt-quench approach [1]. The structure was characterized by means of the radial (pair) distribution function and the bond-angle distribution and the electronic density of states was calculated. We find that our results agree well with experimental data.

Complex Metallic Alloys (CMAs) are metallic solids of high structural complexity, consisting of large numbers of atoms in their unit cells. Consequences of this structural complexity are manifold and give rise to a variety of exciting physical properties. The impact that such structural complexity may have on the lattice dynamics will be discussed. The surprising dynamical flexibility of Tsai-type clusters with the symmetry breaking central tetrahedron will be addressed for Zn6Sc, while in the Ba-Ge-Ni clathrate system the dynamics of encaged Ba guest atoms in the surrounding Ge-Ni host framework is analysed with respect to the experimentally evidenced strong reduction of lattice thermal conductivity. For both systems experimental results from neutron scattering are analyzed and interpreted on atomistic scale by means of ab initio and molecular dynamics simulations, resulting in a picture with the respective structural building blocks as the origin of the peculiarities in the dynamics.

Strategies are described for modeling the kinetics of non-equilibrium film growth during deposition of metals on quasicrystalline substrates. We review previous atomistic-level lattice-gas modeling and Kinetic Monte Carlo simulation for pseudomorphic (or commensurate) submonolayer growth based on a “disordered or irregular bond-network” (DBN) of neighboring adsorption sites. We describe extensions to treat strain effects and multilayer growth, and discuss a type of commensurate-incommensurate transition expected around 2-3 layers. We also describe a coarse-grained “step dynamics” modeling which tracks the dynamics of island edges in each layer rather than individual atoms. Step dynamics models can also include key aspects of the physics such as layer-dependent energetics, including quantum size effects, and strain effects.

Based on X-ray photoelectron spectroscopy, Gd5Ge4(010) does not show evidence of surface segregation. Scanning tunneling microscopy reveals two types of terraces which alternate laterally on the surface. From the step heights, these two surface terminations are assigned as dense, Gd-pure layers in the bulk structure. There is evidence of reconstruction on one type of terrace.

In this work, composites consisting of the Al 2024 matrix reinforced with β-Al3Mg2 particles have been produced by powder metallurgy with the aim of increasing the strength of the matrix and, at the same time, reducing the density of the material. The β-Al3Mg2 phase represents an ideal candidate as reinforcement in lightweight composites due to its low density and high-temperature strength. The β-Al3Mg2 reinforcement remarkably improves the mechanical properties of the 2024 matrix. In particular, the composite with 20 vol.% reinforcement display yield and compressive strengths exceeding that of the unreinforced matrix by about 120 and 180 MPa, while retaining appreciable plastic deformation of about 30 %. The strength of the material is further increased for the samples with 30 and 40 vol.% of β-Al3Mg2 phase, however, the composites show reduced plastic deformation of 11 and 4.5 %. Furthermore, the addition of the low-density β-Al3Mg2 particles decreases the density of the materials below that of the unreinforced 2024 matrix, considerably increasing the specific strength of the composites.

Transport properties (thermal conductivity, electrical resistivity and thermopower) of decagonal quasicrystal d-AlCoNi, and approximant phases Y-AlCoNi, o-Al13Co4, m-Al13Fe4, m-Al13(Fe,Ni)4 and T-AlMnFe have been reviewed. Among all presented alloys the stacking direction (periodic for decagonal quasicrystals) is the most conductive one for the charge and heat transport, and the in/out-of-plane anisotropy is much larger than the in-plane anisotropy. There is a strong relationship between periodicity length along stacking direction and anisotropy of transport properties in both quasicrystals and their approximants suggesting a decrease of the anisotropy with increasing number of stacking layers.

Recent exploratory syntheses of polar intermetallic compounds containing gold have established gold’s tremendous ability to stabilize new phases with diverse and fascinating structural motifs. In particular, Au-rich polar intermetallics contain Au atoms condensed into tetrahedra and diamond-like three-dimensional frameworks. In Au-poor intermetallics, on the other hand, Au atoms tend to segregate, which maximizes the number of Au-heteroatom contacts. Lastly, among polar intermetallics with intermediate Au content, complex networks of icosahedra have emerged, including discovery of the first sodium-containing, Bergman-type, icosahedral quasicrystal. Gold’s behavior in this metal-rich chemistry arises from its various atomic properties, which influence the chemical bonding features of gold with its environment in intermetallic compounds. Thus, the structural versatility of gold and the accessibility of various Au fragments within intermetallics are opening new insights toward elucidating relationships among metal-rich clusters and bulk solids.

The structure of the (100) surface of the orthorhombic Al13Co4quasicrystalline approximant is described based on a combined scanning tunneling microscopy (STM), low-energy electron diffraction (LEED), and density functional theory (DFT) study. We discuss the interplay between the surface structure and the cluster substructure of this approximant as well as possible off-stoichiometry effects that could explain the discrepancies found in the literature on possible surface models.

Metadislocations are highly complex and pivotal defects mediating plastic deformation in complex metallic alloys. Here, we review recent results on the structure of metadislocations in the phases T-Al-Mn-Pd, T-Al-Mn-Fe and o-Al13Co4. In these materials, metadislocation motion is of particular interest as it takes place by pure glide in contrast to most other complex metallic alloys. Recently, novel metadislocations were found in the T-phase [1]. They have Burgers vectors ${\rm{\vec b}} = \pm \tau ^{ - n} c\left( {\matrix{ 0 & 0 & 1 \cr } } \right)$ (n = 2, 3, 4) and are associated to two, four and six planar defects, respectively. The type of planar defect depends on the deformation geometry. Metadislocation glide creates (1 0 0) stacking faults and climb creates (0 0 1) phason planes. Metadislocation glide was observed in the o-Al13Co4 phase, as well [2]. The close structural relation of metadislocations in the phases T-Al-Mn-Pd, T-Al-Mn-Fe, Al13Co4 and ε6-Al-Pd-Mn is discussed.

The δ-FeZn10 phase possesses high structural complexity typical of complex metallic alloys: a giant unit cell comprising 556 atoms, polyhedral atomic order with icosahedrally-coordinated environments, fractionally occupied lattice sites and statistically disordered atomic clusters that introduce intrinsic disorder into the structure. The electrical resistivity is large and exhibits a maximum at about 220 K. The magnetoresistance is sizeable, amounting to 1.5 % at 2 K in 9 T field. The temperature–dependent resistivity is discussed within the frame of the theory of slow charge carriers, applicable to metallic systems with weak dispersion of the electronic bands, where the electron motion changes from ballistic to diffusive upon heating. A comparison to the theory of weak localization is also made.

The Al2Cu and Al9Co2 intermetallic compounds share structural similarities: they are bothdescribed in terms of coordination polyedra with a tetragonal symmetry and covalent-like bonding occur in both compounds. In this paper, the (001) surface structure of Al2Cu and Al9Co2 is described based on a combined scanning tunneling microscopy (STM), low-energy electron diffraction (LEED), X-ray and ultraviolet photoemission spectroscopy (XPS and UPS) and density functional theory (DFT) study. Surface models are elaborated from stoichiometric ideal compounds, leading to a pure aluminium plane as the surface termination in both cases. The nature of the constitutional defect in Al9Co2 is determined using density functional theory calculations. The influence of the surface atomic density, of the surface composition and of off-stoichiometric effects on the (001) surface structures of Al2Cu and Al9Co2 are discussed.