Anisotropic elasticity, electronic structure and thermodynamic properties of Al-Fe-Si intermetallic compounds from first principles calculations

Abstract

In this paper, structural stability, elastic properties, electronic structure and thermodynamic properties of Al-Fe-Si compounds are systematically investigated by first-principles calculations. The negative formation enthalpy indicates that all Al-Fe-Si compounds are thermodynamically stable, and the Al-Fe-Si compounds are determined to be mechanically stable by the stability criteria. The bulk, shear and Young's moduli as well as Poisson's ratio of Al-Fe-Si compounds are also calculated. The results show that Al2Fe3Si3 has the highest shear modulus and Young's modulus, which leads to stronger shear deformation resistance and stiffness. The elastic anisotropy and shear anisotropic factors of Al-Fe-Si compounds are analyzed in this study, and the anisotropy of Al3Fe2Si3 is the greatest among them. Al3Fe2Si3 and Al2Fe3Si4 show metallic character and Al2Fe3Si3 is classified as direct band gap semiconductors. The DOS of Al-Fe-Si compounds are found mainly from Al 3p, Si 3p and Fe 4d states and the Fe-Al/Si bonding is much stronger than that of Al-Si. According to the results, Al2Fe3Si3 has the highest Debye temperature, indicating strong chemical bonding and higher thermal conductivity, which are consistent with the results of Young's modulus and minimum thermal conductivity.