An Ab Initio study of thermodynamic and mechanical stability of Heusler-Based Fe2AlCo polymorphs

0493546 - ÚFM 2019 RIV CH eng J - Journal Article
Friák, Martin - Oweisová, Sabina - Pavlů, Jana - Holec, D. - Šob, Mojmír
An Ab Initio study of thermodynamic and mechanical stability of Heusler-Based Fe2AlCo polymorphs.
Materials. Roč. 11, č. 9 (2018), č. článku 1543. E-ISSN 1996-1944
R&D Projects: GA ČR(CZ) GA17-22139S
Institutional support: RVO:68081723
Keywords : Ab initio * AlCoFe2 * AlFe2Co * CoAlFe2 * Disorder * Elasticity * Fe2CoAl * Heusler * Stability
OECD category: Condensed matter physics (including formerly solid state physics, supercond.)
Impact factor: 2.972, year: 2018

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 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 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.
Permanent Link: http://hdl.handle.net/11104/0288131