Berlin 2008 – wissenschaftliches Programm

Bereiche | Tage | Auswahl | Suche | Downloads | Hilfe

MM: Fachverband Metall- und Materialphysik

MM 37: Intermetallic Phases II

MM 37.4: Vortrag

Donnerstag, 28. Februar 2008, 11:00–11:15, H 0111

Stability range of the B2 NiAl phase investigated by a ternary Cluster-Expansion — •Daniel Lerch, Kerrin Dössel, and Stefan Müller — Lehrstuhl für Festkörperphysik, Universität Erlangen-Nürnberg, Staudtstr. 7, D-91058 Erlangen

The strongly ordering B2 phase of the intermetallic compound NiAl is known to be stable for a broad concentration range off its ideal 1:1 stoichiometry. Evidently this is due to the existence of constitutional defects. Experimental studies have shown that the dominant defect types in Al rich and Al poor parts of the B2 phase are Ni vacancies and Ni antisites (Ni atoms on the Al sublattice) respectively.

We have performed an ab-initio study using a ternary cluster-expansion (CE) based on density functional theory (DFT) calculations. In connection with Monte-Carlo methods, this is an excellent tool to elucidate short-ranged order of defects at finite temperatures, which will be presented here. The results give rise to doubts, whether the stability region of B2 NiAl is indeed as broad as shown in phase diagrams.

This work is supported by the "Studienstiftung des deutschen Volkes" which is gratefully acknowledged.