Dresden 2009 – wissenschaftliches Programm

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MM: Fachverband Metall- und Materialphysik

MM 5: Materials Design I

MM 5.4: Vortrag

Montag, 23. März 2009, 11:00–11:15, IFW D

The free energy of iron: Integrated ab initio derivation of vibrational, electronic, and magnetic contributions — •Fritz Körmann, Alexey Dick, Blazej Grabowski, Tilmann Hickel, and Jörg Neugebauer — Max-Planck-Institut für Eisenforschung GmbH, D-40237, Düsseldorf, Germany

In this talk we present our recently developed [1] integrated ab initio approach including vibrational, electronic, and magnetic contributions to derive the thermodynamic properties of ferromagnetic bcc iron. The quasiharmonic approximation and finite-temperature density functional theory are employed to account for vibrational and electronic excitations. In particular the magnetic contribution to the free energy, which is of crucial importance for the structural phase stability in iron, will be discussed. This contribution has been derived by generalizing an existing many-body theory for the S=1/2 ferromagnet to arbitrary spin quantum numbers and to non-collinear magnetic configurations where the latter is of particular importance for the fcc phase. This approach has lead to an excellent agreement with available experimental data for bcc iron.

[1] F. Körmann, A. Dick, B Grabowski, B. Hallstedt, T. Hickel, and J. Neugebauer, Phys. Rev. B 78, 033102 (2008).