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Materials (Basel). 2018 Aug 27;11(9). pii: E1543. doi: 10.3390/ma11091543.

An Ab Initio Study of Thermodynamic and Mechanical Stability of Heusler-Based Fe₂AlCo Polymorphs.

Author information

1
Institute of Physics of Materials, Academy of Sciences of the Czech Republic, Žižkova 22, CZ-616 62 Brno, Czech Republic. friak@ipm.cz.
2
Institute of Physics of Materials, Academy of Sciences of the Czech Republic, Žižkova 22, CZ-616 62 Brno, Czech Republic. 394665@mail.muni.cz.
3
Department of Chemistry, Faculty of Science, Masaryk University, Kotlářská 2, CZ-611 37 Brno, Czech Republic. 394665@mail.muni.cz.
4
Institute of Physics of Materials, Academy of Sciences of the Czech Republic, Žižkova 22, CZ-616 62 Brno, Czech Republic. houserova@chemi.muni.cz.
5
Department of Chemistry, Faculty of Science, Masaryk University, Kotlářská 2, CZ-611 37 Brno, Czech Republic. houserova@chemi.muni.cz.
6
Central European Institute of Technology, CEITEC MU, Masaryk University, Kamenice 5, CZ-625 00 Brno, Czech Republic. houserova@chemi.muni.cz.
7
Department of Physical Metallurgy and Materials Testing, Franz-Josef-Strasse 18, A-8700 Leoben, Austria. david.holec@unileoben.ac.at.
8
Institute of Physics of Materials, Academy of Sciences of the Czech Republic, Žižkova 22, CZ-616 62 Brno, Czech Republic. mojmir@ipm.cz.
9
Department of Chemistry, Faculty of Science, Masaryk University, Kotlářská 2, CZ-611 37 Brno, Czech Republic. mojmir@ipm.cz.
10
Central European Institute of Technology, CEITEC MU, Masaryk University, Kamenice 5, CZ-625 00 Brno, Czech Republic. mojmir@ipm.cz.

Abstract

We use quantum-mechanical calculations to test a hypothesis of Glover et al. (J. Mag. Mag. Mater. 15 (1980) 699) that Co atoms in the Fe 2 AlCo compound have on average 3 Fe and 3 Co atoms in their second nearest neighbor shell. We have simulated four structural configurations of Fe 2 AlCo including the full Heusler structure, inverse Heusler polymorph and two other 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 Glover and et al. However, small energy differences among three of the studied polymorphs lead to a disordered CsCl-structure-like (B2-like) phase at elevated temperatures. The fourth variant, the full Heusler phase, is predicted to be mechanically unstable. The global magnetic states 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.

KEYWORDS:

AlCoFe2; AlFe2Co; CoAlFe2; Fe2CoAl; Heusler; ab initio; disorder; elasticity; stability

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