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MM: Metall- und Materialphysik
MM 31: Symposium Materials Modelling I
MM 31.3: Talk
Thursday, March 30, 2006, 11:00–11:15, IFW A
Ordering and correlation of cluster orientations in CaCd6 — •Peter Brommer1, Franz Gähler1, and Marek Mihalkovič2 — 1Unversität Stuttgart, Institut für Theoretische und Angewandte Physik, 70550 Stuttgart, Germany — 2Slovak Academy of Sciences, Institute of Physics, 84511 Bratislava, Slovakia
Cadmium and Calcium form a wide variety of complex alloy phases up to an icosahedral quasicrystal. The 1/1 approximant, a bcc arrangement of multi-shelled clusters, shows an order-disorder transition at around 100 K, probably caused by reorientation of the innermost, tetrahedral shell. We use molecular dynamics and EAM potentials generated by force matching to study this transition. Firstly, we isolated the 48 optimal locations for the tetrahedron atoms, out of which four are occupied. We then determined the ground state of a single cluster. From experiment it is known that the tetrahedron orientation in neighbouring clusters is correlated. By developing an effective cluster bond Hamiltonian we can explain the ordering and correlation of the cluster orientations in CaCd6.