Ab Initio Study of Martensitic Transition in Ni2MnGa

T. Koubskýa, P. Sedlákb, H. Seinerb, J. Fojtíkováa, M. Obatac, T. Odac, L. Kalvodaa aDepartment of Solid State Engineering, Faculty of Nuclear Sciences and Physical Engineering, Czech Technical University in Prague, Trojanova 13, 120 00 Prague 2, Czech Republic bInstitute of Thermomechanics, Academy of Sciences of the Czech Republic, Dolejškova 5, 182 00 Prague 8, Czech Republic cDepartment of Computational Science, Institute of Science and Engineering, Kanazawa University, Kakuma, Kanazawa 920-1192, Japan

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Ferromagnetic shape memory alloys are modern functional materials capable of undergoing significant reversible strains induced by moderate external magnetic fields due to diffusionless structural transitions and highly mobile twin interfaces. The subject of our work is a theoretical study of the Ni-Mn-Ga alloy, as a representative of the magnetic shape memory alloys, by means of the ab initio simulation methods. It has been shown that the DFT+U method (the Hubbard treatment of the strong on-site Coulomb interaction of localized electrons) used for description of transition metals, can improve quantitative agreement of theoretical and experimental data. The choice of U-parameters for both Mn and Ni atoms was proposed based on the comparison of experimental and theoretical elastic constants of cubic austenite and tetragonal non-modulated martensite. The resulting theoretical results agree with the elasticity measurements. It has been also shown that involving U-correction have strong impact on the predicted formation energies of particular phases.

DOI:10.12693/APhysPolA.134.804 topics: magnetic shape-memory alloys, Ni-Mn-Ga, density functional theory, DFT+U, elastic constants