Berlin 2005 – wissenschaftliches Programm
Bereiche | Tage | Auswahl | Suche | Downloads | Hilfe
M: Metallphysik
M 20: Intermetallische Phasen I
M 20.4: Vortrag
Samstag, 5. März 2005, 10:00–10:15, TU H2038
Long-periodic superlattices in Cu-rich Cu-Pd alloys - an ab-initio study — •S. Bärthlein1, G.L.W. Hart2, A. Zunger3, and S. Müller1 — 1Festkörperphysik, Universität Erlangen-Nürnberg, Staudtstr. 7, D-91058 Erlangen — 2Department of Physics and Astronomy, Northern Arizona University, Flagstaff, Arizona 86011-6010 — 3National Renewable Energy Laboratory, Golden, Colorado 80401
Beside the well-known L12-phase, Cu-rich Cu-Pd alloys form one- and two-dimensional long-periodic superlattices (LPS). Combining total-energy DFT calculations, a mixed-space cluster-expansion (CE) and genetic algorithms [1], we construct effective multibody interactions, allowing for a detailed study of the structure and stability of these LPS-phases. In good agreement with experiment, at 25% Pd a subtle hierarchy of LPS-structures is found with the so-called LPS3-structure as T=0K ground state, not just being an entropically stabilized feature. With the help of Monte-Carlo simulations, phase transition temperatures and short-range order behaviour (SRO) are predicted. Hereby, the SRO-pattern of the LPS-phase shows a four-fold peak-splitting at ⟨110⟩ and a two-fold one at ⟨100⟩, allowing for a determination of the Fermi-vector. The results are in excellent agreement with experimental data. (Supported by DFG.)
[1] G.L.W. Hart et al., submitted (2004)