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MM: Fachverband Metall- und Materialphysik

MM 39: Structural Materials (Steels, light-weight materials, high-temperature materials)

MM 39.7: Vortrag

Donnerstag, 4. April 2019, 17:15–17:30, H45

A quantum-mechanical study of thermodynamic and mechanical stability of Heusler-based Fe₂AlCo polymorphs — •Martin Friák¹, Sabina Oweisová^1,2, Jana Pavlů^3,2,1, David Holec⁴, and Mojmír Šob^2,1,3 — ¹Institute of Physics of Materials, Academy of Sciences of the Czech Republic, Brno, Czech Republic — ²Department of Chemistry, Faculty of Science, Masaryk University, Brno, Czech Republic — ³Central European Institute of Technology, CEITEC MU, Masaryk University, Brno, Czech Republic — ⁴Department of Materials Science, Montanuniversität Leoben, Leoben, Austria

We use quantum-mechanical calculations to test a hypothesis of Grover et al. (J. Mag. Mag. Mater. 15 (1980) 699) that Co atoms in the Fe₂AlCo compound have on average 3 Fe and 3 Co atoms in their second nearest neighbor shell. We have simulated four structural configurations of Fe₂AlCo including the full Heusler structure, inverse Heusler polymorph and two phases matching this idea. The highest thermodynamic stability at T = 0 K is indeed predicted for one of the phases with the distribution of atoms according to Grover and co-workers. However, small energy differences among three of the studied polymorphs lead to a disordered B2-like phase at elevated temperatures. The fourth variant, the full Heusler phase, is predicted to be mechanically unstable. All studied variants are predicted to be ferromagnetic but local magnetic moments of Fe and Co atoms sensitively depend on the composition of the first and second coordination shells. For details see Materials 11 (2018) 1543, doi: 10.3390/ma11091543.