Elastic properties of Ni 2MnGa from first-principles calculations

• Published in: Journal of alloys and compounds Vol. 508; no. 1; pp. 177 - 183
• Main Authors: Ozdemir Kart, S., Cagın, T.
• Format: Journal Article
• Language: English
• Published: Elsevier B.V 2010
• Subjects: Debye temperature; Elastic constants; Magnetic shape memory alloy; Debye temperature; Elastic constants; Magnetic shape memory alloy
• ISSN: 0925-8388; 1873-4669
• DOI: 10.1016/j.jallcom.2010.08.039

In this study, we have performed spin-polarized total energy calculations aiming to develop microscopic understanding of magnetic shape memory behavior of Ni 2MnGa. This paper is devoted to determine the mechanical properties of Ni 2MnGa in both austenitic and martensitic structures. To the best of our knowledge, this work presents the elastic constants of Ni 2MnGa in the structure of 5M martensite, for the first time. We have also re-calculated elastic constants for cubic and nonmodulated (NM) structures by using the potential with e/ a = 7.5. The elastic constants are predicted by straining the cubic L2 1, 5M pseudo-tetragonal and NM tetragonal martensitic structures. Because of the special significance of the isotropic bulk modulus, shear modulus, Young's modulus and Poisson's ratio for technological applications, we have also calculated these quantities from the elastic constants. Elastic properties of Ni 2MnGa in both austenitic and martensitic structures are determined by using ab initio methods based on density functional theory (DFT) within the spin-polarized generalized-gradient approximation. The tetragonal shear elastic constant C′ takes a very small value in the austenitic phase, indicating the elastic instability results in a phase transition to martensitic structure. Isotropic mechanical properties such as bulk modulus, shear modulus, Young's modulus and Poisson's ratio are predicted. The trend of the Debye temperatures calculated for three structures of Ni 2MnGa is comparable with that of the experiment.