Regensburg 2013 – wissenschaftliches Programm
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MM: Fachverband Metall- und Materialphysik
MM 8: Topical Session: Quasicrystals & Complex Metallic Alloys II
MM 8.2: Vortrag
Montag, 11. März 2013, 12:00–12:15, H25
Confirmation of the Random Tiling Hypothesis for a Decagonal Quasicrystal — •Alexander Kiselev1, Michael Engel2, and Hans-Rainer Trebin1 — 1Institut für Theoretische und Angewandte Physik, Universität Stuttgart, Germany — 2Department of Chemical Engineering, University of Michigan, USA
The random tiling hypothesis of Henley and Elser states, that the configurational entropy due to the phason flips stabilizes a quasicrystal at elevated temperatures and leads to a periodic crystal at low temperatures. Here, we study the role of entropy for a monatomic two-dimensional decagonal model quasicrystal, whose atoms interact by a double-well Lennard-Jones-Gauss pair potential. We calculate the free energy of the system, which can be split up into a phonon part and a configurational part. The phonon part of the free energy is calculated with molecular dynamics using the Frenkel-Ladd method. For the configurational part a new Ising-type model of uncorrelated flips is employed in Monte Carlo simulations. We observe that the free energy takes a square-gradient form of the phason displacement as predicted by the random tiling hypothesis and determine phason elastic constants over a large range of temperatures. The free energy calculations confirm a phase transition from an entropically stabilized decagonal random tiling phase to an energetically stabilized periodic crystal. Thus, for the first time, a virtual quasicrystal confirms all predictions of the random tiling hypothesis in a fully atomistic model [1].
[1] A. Kiselev, M. Engel and H.-R. Trebin, arXiv:1210.4227 (2012)