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Effect of electron localization in theoretical design of Ni-Mn-Ga based magnetic shape memory alloys

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    0543903 - ÚT 2022 RIV GB eng J - Journal Article
    Zelený, M. - Sedlák, Petr - Heczko, Oleg - Seiner, Hanuš - Veřtát, Petr - Obata, M. - Kotani, T. - Oda, T. - Straka, Ladislav
    Effect of electron localization in theoretical design of Ni-Mn-Ga based magnetic shape memory alloys.
    Materials and Design. Roč. 209, November (2021), č. článku 109917. ISSN 0264-1275. E-ISSN 1873-4197
    R&D Projects: GA ČR(CZ) GA21-06613S; GA MŠk(CZ) LM2018096
    Institutional support: RVO:61388998 ; RVO:68378271
    Keywords : martensitic transformation * magnetic shape memory alloys * phase stability * electron localization * Ab initio calculations * exchange-correlation energy
    OECD category: Condensed matter physics (including formerly solid state physics, supercond.); Condensed matter physics (including formerly solid state physics, supercond.) (FZU-D)
    Impact factor: 9.417, year: 2021
    Method of publishing: Open access

    The precise determination of the stability of different martensitic phases is an essential task in the successful design of (magnetic) shape memory alloys. We evaluate the effect of electron delocalization correction on the predictive power of density functional theory for Ni-Mn-Ga, the prototype magnetic shape memory compound. Using the corrected Hubbard-model-based generalized gradient approximation (GGA+U), we varied the Coulomb repulsion parameter U from 0 eV to 3 eV to reveal the evolution of predicted material parameters. The increasing localization on Mn sites results in the increasing stabilization of 10M modulated structure in stoichiometric Ni2MnGa in agreement with experiment whereas uncorrected GGA and meta-GGA functional provide the lowest energy for 4O modulated structure and non-modulated structure, respectively. GGA+U calculations indicate that 10M structure is more stable than other martensitic structures for U > 1.2 eV. The key features of density of states (DOS) responsible for the stabilization or destabilization of particular martensitic phases calculated with GGA+U are found also in DOS calculated with advanced quasi-particle self-consistent GW (QSGW) method. It supports the physical background of Hubbard correction. Moreover, the calculations with U = 1.8 eV provide the best agreement with experimental data for lattice parameters of stoichiometric and off-stoichiometric alloys.
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