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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. Sanchez2 — 1Max-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.