SKM 2021 – wissenschaftliches Programm

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MM: Fachverband Metall- und Materialphysik

MM 6: Topical Session Interface-Dominated Phenomena - Thermodynamics

MM 6.3: Vortrag

Mittwoch, 29. September 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 Friák^1,2, Miroslav Černý^2,3, and Mojmír Šob^4,1 — 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.