Comparative Study on Electronic Structure and Optical Properties of α-Fe2O3, Ag/α-Fe2O3 and S/α-Fe2O3

The electronic structures and optical properties of pure, Ag-doped and S-doped alpha-Fe2O3 were studied using density functional theory (DFT). The calculation results show that the structure of alpha-Fe2O3 crystal changes after Ag and S doping, which leads to the different points of the high symmetry of Ag-doped and S-doped alpha-Fe2O3 with that of pure alpha-Fe2O3 in the energy band, as well as different Brillouin paths. In addition, the band gap of alpha-Fe2O3 becomes smaller after Ag and S doping, and the optical absorption peak shifts slightly toward the short wavelength, with the increased peak strength of S/alpha-Fe2O3 and the decreased peak strength of Ag/alpha-Fe2O3. However, the optical absorption in the visible range is enhanced after Ag and S doping compared with that of pure alpha-Fe2O3 when the wavelength is greater than 380 nm, and the optical absorption of S-doped alpha-Fe2O3 is stronger than that of Ag-doped alpha-Fe2O3.