Berlin 2012 – wissenschaftliches Programm
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MM: Fachverband Metall- und Materialphysik
MM 17: Poster Session
MM 17.9: Poster
Montag, 26. März 2012, 17:00–19:00, Poster B
From structure refinements of ε-Al–Pd–Mn phases toward decagonal quasicrystals — •Benjamin Frigan1, Marek Mihalkovič2, and Hans-Rainer Trebin1 — 1Institut für Theoretische und Angewandte Physik, Universität Stuttgart, Germany — 2Institute of Physics, Slovak Academy of Sciences, Bratislava, Slovakia
We have studied and resolved occupancy correlations in the existing average structure model of the complex metallic alloy ξ′-Al–Pd–Mn, which has approximately 320 atoms in the unit cell and many fractionally occupied sites. Model variants were constructed systematically in a tiling-decoration approach and subjected to simulated annealing by use of both density functional theory and molecular dynamics with empirical potentials.
The main structural building blocks of ξ′ are pseudo-Mackay icosahedral (PMI) clusters which form columns parallel to (0,1,0) and when projected are vertices of a hexagonal tiling. The tiling representation allows to extend structure models for the ξ′-phase to structure models of other closely related phases where the projections of the PMI columns also form pentagon and nonagon tiles. Our refined tiling-decoration model applies to any structure within the so-called ε-phases family.
We further extend our tiling-decoration model and present a detailed atomistic description of all tiles that are observed in the decagonal quasicrystalline phase. We show how aspects of both the ε-phases and the decagonal phase can serve as a starting point for an accurate microscopic modeling of the metadislocations.