First-principles study on stability, Debye temperature, mechanical, electronic and magnetic properties of Fe2B compounds

In this work, the stability, Debye temperature, mechanical, electronic and magnetic properties of four kinds of Fe2B with the different crystal structures were investigated by first-principles calculation, and the results of Fe2B with or without spin polarization were comparatively analyzed. It was found that spin polarization increases the thermodynamic stability and Debye temperature of T-1 (ICSD NO: 30446) and T-2 (42530), but reduces that of T-3 (16809) and T-4 (160789). Only T-1 and T-2 are thermodynamically stable compounds, but all of the Fe2B are mechanically stable. Ferromagnetic T-1 and T-2 have the largest Young's modulus, shear modulus, Vickers hardness and fracture toughness. Moreover, their Vickers hardness is much larger than that of the others. Electronic structures revealed that the larger modulus (B, E and G) of T-1 and T-2 originate from their stronger Fe-Fe bonds and/or weaker elastic anisotropy. The Ms of unit cell of T-3 and T-4 are larger than that of T-1 and T-2. Thus, ferromagnetic T-1 and T-2 can be considered as the excellent candidates for high-performance wear-resistance materials and strong ferromagnetic materials with high hardness, whereas the T-3 and T-4 are just suitable for the application of strong ferromagnetic materials without wear.