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M: Metallphysik

M 32: Intermetallische Phasen II

M 32.1: Vortrag

Mittwoch, 26. März 2003, 16:30–16:45, IFW B

First-principles investigation of the NiFeAl system — •Frank Lechermann1, Manfred Fähnle1, and Juan M. Sanchez21Max-Planck-Institut für Metallforschung, Heisenbergstr. 3, D-70569 Stuttgart — 2Texas Materials Institute, The University of Texas at Austin, Texas 78712, USA

By combining ab-initio electron theory and statistical mechanics we investigated the rich physics of the intermetallic system NiFeAl. This technological important system shows not only an distinct interplay between magnetism and structure over a wide composition range, but exhibits also weakly correlated aluminides which are challenging for modern electronic structure methods.
We performed density functional calculations for various structures on the bcc and fcc lattice with and without the inclusion of collinear magnetism, and mapped the yielded formation energies via the cluster expansion (CE) onto a set of many-body interactions. Then the cluster variation method in tetrahedron approximation was used to determine the ternary phase diagram at finite temperatures. Thereby, we were able to identify a miscibility gap in the ternary B2 phase. This result and other features of the phase diagram will be discussed.
Additionally, we extended the CE for the bcc lattice to higher clusters by using the ab-inito calculated formation energies of more than hundred structures. The herefrom exctracted important information about the energetics in the NiFeAl system will be presented, too.
Support by the DFG is gratefully acknowledged.

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DPG-Physik > DPG-Verhandlungen > 2003 > Dresden