SKM 2021 – scientific programme
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MM: Fachverband Metall- und Materialphysik
MM 6: Topical Session Interface-Dominated Phenomena - Thermodynamics
MM 6.3: Talk
Wednesday, September 29, 2021, 10:45–11:00, H8
A quantum-mechanical study of impact of vibrational entropy on the segregation of Cu to antiphase boundaries in Fe3Al — •Martin Friák1,2, Miroslav Černý2,3, and Mojmír Šob4,1 — 1Institute of Physics of Materials, Czech Academy of Sciences, Brno, Czech Republic — 2Central European Institute of Technology (CEITEC), Brno University of Technology, Brno, Czech Republic — 3Faculty of Mechanical Engineering, Brno University of Technology, Brno, Czech Republic — 4Department of Chemistry, Faculty of Science, Masaryk University, Brno, Czech Republic
We have performed an ab initio study of segregation of Cu atoms towards antiphase boundaries (APBs) in Fe3Al. The Cu atoms are predicted to segregate towards the studied APBs (the APB energy is then equal to 84 mJ/m2) but the related energy gain is only 4 meV per Cu atom. Both Cu atoms (as point defects) and APBs (as extended defects) have their specific impact on local magnetic moments of Fe atoms (and they non-linearly combine when both types of defects are present). We have also performed phonon calculations and found all studied states mechanically stable. The band gap in phonon frequencies of Fe3Al is barely affected by Cu substituents but reduced by APBs. The phonon contributions into segregation-related energy changes are significant, ranging from a decrease by 16 % at T = 0 K to an increase by 17 % at T = 400 K (changes with respect to the segregation-related energy difference between static lattices). Further, we have found non-linear trends in changes induced by the Cu segregation in the phonon entropy and phonon energy.