Interatomic force interaction in an i-AlCuFe quasicrystal
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ICRYSTALS
Interatomic Force Interaction in an i-AlCuFe Quasicrystal P. P. Parshina, M. G. Zemlyanova, and R. A. Brandb a
Russian Research Centre Kurchatov Institute, pl. Akademika Kurchatova 1, Moscow, 123182 Russia e-mail: [email protected] b Gerhard Mercator University Duisburg, D-47048 Duisburg, Germany Received March 29, 2007
Abstract—Partial spectra of thermal vibrations of Al, Cu, and Fe atoms in an icosahedral quasicrystal have been obtained by the isotopic-contrast method in inelastic neutron scattering. Joint analysis of these results and the published data on the atomic and electronic structures of the icosahedral i-AlCuFe quasicrystal has been performed. A physical model of the quasicrystal structure is proposed that is in agreement with the existing experimental data and qualitatively describes the peculiarities of interatomic interaction. PACS numbers: 63.22.+m, 63.50.+x, 63.90.+t DOI: 10.1134/S1063774507060144
INTRODUCTION The combination of unique physicochemical properties of quasicrystalline alloys [1, 2] is naturally of great interest for researchers and stimulates investigations in this field that are aimed, on the one hand, at determining the origin of these unusual properties and, on the other hand, at analyzing the possibilities of practical application of quasicrystals and improvement of the their synthesis techniques. Generally, stable quasicrystalline phases are synthesized in ternary systems of metallic elements (involving transition metals). In particular, typical representatives of icosahedral quasicrystals (with six fivefold symmetry axes) is the Al0.62Cu0.255Fe0.125 alloy. In the most general form, the atomic structure of quasicrystals can be represented as a network of interpenetrating, quasi-periodically packed clusters, whose diameter amounts to several interatomic distances. In the case of icosahedral quasicrystals, these atomic clusters are composed of icosahedral and dodecahedral shells, which have fivefold symmetry axes [3]. The presence of narrow peaks in the electron [4], X-ray [5], and neutron [6] diffraction patterns of quasicrystals indicates the presence of long-range order in the arrangement of atoms in these alloys. At the same time, the spatial periodicity is absent because it is inconsistent with the presence of fivefold symmetry axes. At the microscopic level, investigations of the interatomic force interactions in quasicrystals are of interest. It is not inconceivable that the unusual structure and properties of quasicrystals are related to a large extent to the peculiarities of interatomic interaction, which manifest themselves in the spectra of thermal atomic vibrations. Thus, detailed information about these spectra is necessary as a basis for developing adequate models of interatomic force interaction and, therefore, for
understanding many physical properties of quasicrystals. A direct method for obtaining such information is inelastic scattering of slow neutrons with application of the isotopic-contrast method. In this study, to reveal specific features of
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