Stability, electronic structure, mechanical and thermodynamic properties of Fe-Si binary compounds

Abstract

The stability, electronic structure, mechanical and thermodynamic properties of Fe11Si5, Fe2Si, Fe5Si3 (with the Mn5Si3 structure), FeSi, α-FeSi2 and β-FeSi2 (orthorhombic) were systematically investigated by first-principles calculation. Fe2Si, FeSi and β-FeSi2 are thermodynamically stable intermetallic compounds. The electronic structures and chemical bonding were analyzed by the density of states (DOS) and the electron density distribution map. The stress-strain method was used to calculated elastic constants. The mechanical modulus, such as the bulk modulus (B), shear modulus (G) and Young's modulus (E) were discussed. FeSi has the largest shear modulus and Young's modulus as 188.6 GPa and 457.9 GPa, respectively. The ratio of B/G was used as an indicator for the ductility or brittleness of the compounds. The anisotropic index, three-dimensional (3D) surface contour and planar projections on (001) and (110) planes were used to reveal the anisotropy of Young's modulus. Furthermore, the heat capacity and minimum thermal conductivity were studied. Fe11Si5 has the smallest thermal conductivity with 1.81 W m−1K−1. Moreover the temperature-dependent formation enthalpy and entropy were discussed, and the two thermodynamic parameters indicate high temperature decrease the thermodynamic stability of Fe-Si binary compounds.