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Electronic structures and electromagnetic wave absorption properties of Fe3Si/polypyrrole (PPy) composites are investigated by using first principles methods based on plane–wave pseudopotential theory. The calculation of electric structures shows that the Fe3Si/PPy composite presents typical metal properties. The real and imaginary parts of the dielectric constant of Fe3Si/PPy are larger than those of Fe3Si. The maximum absorption coefficient of Fe3Si is larger than that of Fe3Si/PPy, and the maximum absorption coefficients of both materials all increase first and then decrease. However, the variation range of the absorption coefficient of Fe3Si/PPy is wider than that of Fe3Si. The reflection coefficient and maximum extinction coefficient of Fe3Si/PPy are larger than those of Fe3Si. The maximum reflection coefficient of Fe3Si/PPy is greater than that of Fe3Si, and the maximum reflection coefficients of Fe3Si/PPy and Fe3Si are 0.81 and 0.91, respectively. In terms of loss function and refractive index, Fe3Si/PPy has more practical value than Fe3Si.

The electronic structure, and magnetic and dielectric properties of Fe3Si@SiO2 core-shell structure with or without SiO2 outer shell cover have been investigated using first principle calculation based on plane-wave pseudo-potential theory. Results indicate that the Fe3Si@SiO2 core-shell structure exhibits a strong interaction between Fe3Si inner core and SiO2 outer shell. The formation energy (Ef) of Fe3Si@SiO2 indicates that it has a structurally stable state at this time. Fe3Si@SiO2 core-shell structure presents typical metal properties and magnetism in the structural optimization process. Furthermore, the total magnetic moment of each atom of Fe3Si@SiO2 core-shell structure is smaller than that of bulk Fe3Si inner core. The SiO2 covered substance also exhibits strong hybridization between the SiO2 shell and the Fe3Si core surface atoms. Thus, the composite structure exhibits strong dielectric polarization response, which further increases the dielectric loss of the material. The calculation results of dielectric properties show that the conductivity and dielectric constant of the core-shell composite are greatly reduced, thereby improving material impedance matching and wave absorption performance.