Dresden 2011 – wissenschaftliches Programm

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MM: Fachverband Metall- und Materialphysik

MM 33: Topical Session Electron Theory IV

MM 33.5: Vortrag

Donnerstag, 17. März 2011, 12:45–13:00, IFW A

Finite temperature magnetism combining first-principles and spin Quantum Monte Carlo — •Fritz Körmann, Alexey Dick, Tilmann Hickel, and Jörg Neugebauer — Max-Planck-Institut Düsseldorf, Max-Planck-Straße 1, 40074 Düsseldorf

The free energy of a system is a fundamental quantity for predicting phase diagrams, finite temperature materials parameters, or kinetic barriers. An ab initio derivation of it makes a highly accurate evaluation of all excitation processes mandatory. One of the most challenging - but for many engineering materials crucial - contributions arises from the magnetic degrees of freedom. We have developed a mapping procedure that transforms the full magnetic Hamiltonian onto an effective nearest-neighbor spin Hamiltonian. The latter can be directly solved employing spin quantum Monte Carlo calculations. We demonstrate the high accuracy achievable by the new approach by computing magnetic heat capacities and free energies for the magnetic pure elements Fe, Co, and Ni, and by extending it to magnetic compounds such as Cementite (Fe3C) [1]. In all cases, an excellent agreement with experimental data is found.

[1] Hallstedt, Djurovic, von Appen, Dronskowski, Dick, Körmann, Hickel, Neugebauer, Calphad 34, 129 (2010).