Dresden 2006 – wissenschaftliches Programm
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MM: Metall- und Materialphysik
MM 10: Intermetallic phases
MM 10.2: Vortrag
Montag, 27. März 2006, 16:45–17:00, IFW D
Detecting low-temperature intermetallic compounds in the Ag-Pd-system - a first principles study — •E. Winning, S. Bärthlein, and S. Müller — Festkörperphysik, Universität Erlangen-Nürnberg, Staudtstr. 7, D-91058 Erlangen
Similar to Cu-Pd and Au-Pd, Ag-Pd-compounds form long-periodic superlattices (LPS) based on the L12-structure at 25at.% Pd. Experimentally Ag-Pd is known to form mutually miscible disordered solid solutions down to ∼800 K, but at lower temperatures no experimental data is available up to now. With the help of total-energy DFT calculations and a mixed-space cluster-expansion (MSCE) in conjunction with genetic algorithms (GA) [1], effective multi-body interactions are designed, that permit us to study millions of possible ground-states (GS) over the full concentration range. We thus find some new GS compared to earlier studies [2]. Most notably we predict the LPS3 as GS at xPd = 0.25. At xPd = 0.5 we can confirm earlier results by also predicting L11 as ground state, although a similar structure lies almost degenerately above. Like in the case of Cu-Pd 2D- and 3D-LPS are taken into consideration to confirm the LPS3-structure as GS. By applying Monte Carlo simulations we predict the phase transition temperatures and the short-range order behaviour.
[1] G.L.W. Hart et al., Nat. Mater. 4, 391 (2005)
[2] S. Müller and A. Zunger, Phys. Rev. Lett. 87, 165502 (2001)