Exploration of Structural, Thermodynamic, Magnetic, Mechanical, and Dynamical Properties of Martensite Fe3Pt Alloys: A Density Functional Theory Study

Abstract

The current study explored the martensite structures of Fe3Pt alloys, specifically Cmmm-Fe3Pt, P63/mmc-Fe3Pt, P4/mmm-Fe3Pt, and R3¯m-Fe3Pt, aiming to provide a comprehensive understanding of the mechanisms that govern their physical and chemical properties. We have focused on their structural, thermodynamical, magnetic, electronic, mechanical, and dynamical characteristics, utilizing the density functional theory (DFT) technique. Our study revealed that in addition to the previously reported austenitic cubic Pm3¯m-Fe3Pt and martensite tetragonal I4/mmm-Fe3Pt with L12 structure, there exist additional Fe3Pt phases that exhibit excellent structural, thermodynamic, magnetic, and mechanical properties. The calculated enthalpies of formation were found to be negative and less than −0.39 eV in all the structures considered, indicating thermodynamic stability and formation under experimental synthetic conditions. Moreover, the computed magnetic moments are in the range 2.94 to 3.04 μB, which is relatively comparable to 3.24 μB of the widely reported Pm3¯m-Fe3Pt alloy. The analysis of the electronic structure also revealed strong magnetism due to the presence of asymmetry in the spin-up and -down states of the density of states (DOS) plots. To determine the mechanical response of Fe3Pt structures under loading conditions, we computed the independent elastic constants, macroscopic properties, and stress–strain relationship under hydrostatic stress. All four phases were studied, but the hypothetical P63/mmc-Fe3Pt showed excellent mechanical stability at ambient conditions and exceptional hardness and resistance to compression in the elastic region 0% ≤ strain ≤ 10%. This evidence is provided by satisfying the Born necessary stability conditions, large bulk modulus, and a strong linear relationship fit (R2) of greater than 0.94. Moreover, the phonon dispersion curves revealed dynamical stability for Cmmm-Fe3Pt and R3¯m-Fe3Pt, and metastability for P4/mmm-Fe3Pt, while the hypothetical P63/mmc-Fe3Pt is unstable.