Ab initio prediction of stable nanotwin double layers and 4O structure in Ni2MnGa

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Authors

ZELENÝ Martin STRAKA Ladislav SOZINOV Alexei HECZKO Oleg

Year of publication 2016
Type Article in Periodical
Magazine / Source Physical Review B
MU Faculty or unit

Central European Institute of Technology

Citation
Web http://journals.aps.org/prb/abstract/10.1103/PhysRevB.94.224108
Doi http://dx.doi.org/10.1103/PhysRevB.94.224108
Field Solid matter physics and magnetism
Keywords SHAPE-MEMORY ALLOYS; NI-MN-GA; BRILLOUIN-ZONE INTEGRATION; TOTAL-ENERGY CALCULATIONS; AUGMENTED-WAVE METHOD; CRYSTAL-STRUCTURE; MARTENSITIC-TRANSFORMATION; SINGLE-CRYSTALS; HEUSLER ALLOYS; BASIS-SET
Description The ab initio electronic structure calculations of the Ni2MnGa alloy indicate that the orthorhombic 4O structure exhibits the lowest energy compared to all known martensitic structures. The 4O structure is formed by nanotwin double layers, i.e., oppositely oriented nanotwins consisting of two (101) lattice planes of nonmodulated martensitic structure. It exhibits the lowest occupation of density of states at the Fermi level. The total energy 1.98 meV/atom below the energy of nonmodulated martensite is achieved within structural relaxation by shifting Mn and Ga atoms at the nanotwin boundaries. The same atomic shift can also be found in other martensitic nanotwinned or modulated structures such as 10M and 14M, which indicates the importance of the nanotwin double layer for the stability of these structures. Our discovery shows that the nanotwinning or modulation is a natural property of low-temperature martensitic phases in Ni-Mn-Ga alloys.
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