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Journal ArticleDOI

Electronic structure of a quasicrystalline model for Al13Fe4

TL;DR: In this article, a model for the decagonal phase of the Al13Fe4 system is proposed and the electronic structure is calculated within the tight-binding method, and results for the local and the integrated electronic density of states at particular sites are presented.
Abstract: A model for the decagonal phase of the Al13Fe4 system is proposed The electronic structure is calculated within the tight-binding method Results for the local and the integrated electronic density of states at particular sites are presented
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Journal ArticleDOI
11 Jan 2019
TL;DR: In this paper, the intrinsic defects in θ-Al13Fe4 were investigated using a first-principles density-functional theory method, which revealed that among the various intrinsic defects it is energetically favorable for Fe substitution of Al but on just three of the fifteen Al sites.
Abstract: θ-Al13Fe4 exhibits a rich variety of crystal physics. It contains twenty crystallographically different atomic species with a diversity of chemical coordination. An understanding of its structural and physical properties is a prerequisite for controlling its formation and its use. Here we investigate systematically the intrinsic defects in θ-Al13Fe4 using a first-principles density-functional theory method. The calculations reveal that among the various intrinsic defects it is energetically favourable for Fe substitution of Al but on just three of the fifteen Al sites. This results in a new structural model, Al68Fe24 (the Roman numerals represent the Al sites) which updates the thermodynamic model, currently in use, which is associated with the formation of vacancies on some of the Al sites. The calculations demonstrate that the addition of Fe induces magnetism which gives rise to clustering. The calculations provide the dependence of the lattice parameters on Fe concentration and explain the experimental data in the literature. The information obtained here provides insight into the formation and properties of θ-Al13Fe4 and its role in the solidification of Al alloys, in determination of the microstructure and related mechanical properties of the products, and in catalysis for organic reactions.

11 citations

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Journal ArticleDOI
TL;DR: In this article, a metallic solid with long-range orientational order, but with icosahedral point group symmetry, which is inconsistent with lattice translations, was observed and its diffraction spots are as sharp as those of crystals but cannot be indexed to any Bravais lattice.
Abstract: We have observed a metallic solid (Al-14-at.%-Mn) with long-range orientational order, but with icosahedral point group symmetry, which is inconsistent with lattice translations. Its diffraction spots are as sharp as those of crystals but cannot be indexed to any Bravais lattice. The solid is metastable and forms from the melt by a first-order transition.

5,702 citations

Journal ArticleDOI
TL;DR: Studies of phase formation in rapidly solidified Al-Mn alloys show that an icosahedral phase is replaced by another noncrystallographic phase, a decagonal phase.
Abstract: Studies of phase formation in rapidly solidified Al-Mn alloys (composition range 18-22 at.% Mn) show that an icosahedral phase is replaced by another noncrystallographic phase, a decagonal phase. The decagonal phase is another example of quasicrystal: It has a noncrystallographic point group ($\frac{10}{m}$ or $\frac{10}{\mathrm{mmm}}$) together with long-range orientational order and one-dimensional translational symmetry. The decagonal phase is an intermediate phase between an icosahedral phase and a crystal both from the symmetry and from the solidification condition points of view.

527 citations

Journal ArticleDOI
TL;DR: In this paper, a model for the atomic structure of the Al-Mn quasicrystal is proposed, where icosahedral symmetry and its projections onto various planes have a self-similarity property based on the golden number, in agreement with TEM results.
Abstract: A model is proposed for the atomic structure of the Al-Mn quasicrystal. Mn icosahedra are connected through their threefold axes, with a coordination number of seven and each bond defined by an octahedron. This Mn skeleton has icosahedral symmetry and its projections onto various planes have a self-similarity property based on the golden number, in agreement with TEM results. The filling up with A1 atoms determines a sublattice where empty Al icosahedra are connected by chains of three distorted octahedra. Two kinds of Mn-Al first-neighbour environments are distinguished, involving nine and ten Al atoms. Taking the ratio of the two Mn site numbers as equal to the golden number leads to a chemical composition in agreement with X-EDS analysis.

239 citations

Journal ArticleDOI
TL;DR: The electronic structures are calculated for several crystalline approximants of quasicrystals, AlCuLi and AlFe, and the densities of states of these systems, and also of AlMn, suggest universality of the pseudogap at the Fermi energy in quasICrystals.
Abstract: The electronic structures are calculated for several crystalline approximants of quasicrystals, AlCuLi and AlFe. The densities of states of these systems, and also of AlMn, suggest universality of the pseudogap at the Fermi energy in quasicrystals. The pseudogap satisfies a Hume-Rothery--type relation. The origin of the pseudogap is attributed to strong electron scattering by the lattice and the pseudogap causes an enhancement of cohesive energies. The characteristics of the states in the pseudogap and the electric resistivity are also discussed.

198 citations