Dresden 2009 – scientific programme

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MM: Fachverband Metall- und Materialphysik

MM 9: Intermetallic Phases I

MM 9.1: Talk

Monday, March 23, 2009, 14:45–15:00, IFW B

Ab-initio based study of antisite-precipitates in B2-CoAl — •Nils Schindzielorz and Stefan Müller — Universität Erlangen-Nürnberg, Lehrstuhl für Theoretische Physik 2, Staudstr. 7 D-91058 Erlangen

It is well-known that for high temperatures around 1500K the B2-phase of CoAl up to about 70% Co is stabilized by the existence of so called antisite atoms [1]. By quenching the crystal to low temperatures, this phase separates into an ideal B2-CoAl crystal and precipitates consisting of Co antisites only. By the combination of a density functional theory based cluster expansion Hamiltonian with Monte-Carlo simulations it will be demonstrated that these Co clusters show a characteristic size-shape-temperature dependence. Furthermore, we find a flattening of the precipitates at low temperatures due to the anisotropy of the interfacial energy which is wiped out at higher temperature by entropy. A detailed knowledge of the structure of these nanoclusters is of special importance as they lead to local magnetism in a non-magnetic intermetallic compound.
Supported by Deutsche Forschungsgemeinschaft.
V. Blum et al., Phys. Rev. Lett. 89, 266102 (2002)