Berlin 2018 – wissenschaftliches Programm
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MA: Fachverband Magnetismus
MA 7: Focus Session: Magnetism in Materials Science: Thermodynamics, Kinetics and Defects I (joint session MM/MA)
MA 7.4: Vortrag
Montag, 12. März 2018, 11:15–11:30, TC 010
Lattice relaxations in paramagnetic materials from first principles — •Davide Gambino1 and Björn Alling1,2 — 1Department of Physics, Chemistry, and Biology (IFM) Linköping University, SE-58183 Linköping, Sweden — 2Max-Planck-Institut für Eisenforschung GmbH, D-402 37 Düsseldorf, Germany
The first-principles calculation of many material properties starts with the relaxation of the atomic positions of the system under investigation. This procedure is routine for nonmagnetic materials, as well as for magnetically ordered compounds. However, when it comes to magnetically disordered systems, it is not clear what geometry one should take into account. Here we propose a method for the structural relaxation of magnetic materials in the paramagnetic regime within the disordered local moment (DLM) picture in the framework of density functional theory (DFT). The method can be easily implemented using any ab initio code.
We consider as a test case Fe vacancy in bcc Fe in the paramagnetic regime: as a result, the nearest neighbors to the vacancy relax inwards of about 0.16 Angstrom (-5% of the ideal bcc nearest neighbor distance), which is twice as large as the relaxation in the ferromagnetic case, and the vacancy formation energy calculated on these positions results to be 1.60 eV, which corresponds to a reduction of about 0.1 eV compared to the formation energy calculated on ferromagnetic-relaxed positions. Our results are in good agreement with recent DFT+DMFT calculations and with experimental values. Other systems under investigations are interstitial defects in bcc Fe and FeCr random alloys.