First principles study on electronic structure and optical properties of SrI₂ and SrI₂: Eu

Based on the first principle of density functional theory, we study the band structure, electron density and optical properties of SrI₂ and SrI₂: Eu crystals. The exchange and correlation potential is calculated using the first principle of generalized gradient approximation (GGA). Our research results show that the crystal volume of SrI2 after doping has decreased; SrI₂ and SrI₂: Eu crystals have band gaps of 3.909eV and 0.398eV, respectively, indicating that the electrons after doping transition from the valence band to the conduction band require less energy. Judging from the distribution of state density, the peak width of the valence band near the Fermi level increases, and the Eu doping adds a small peak to the valence band near the Fermi level. These phenomena show that doping can produce more visible scintillating photons when exposed to the same radiation. SrI₂ and SrI₂: Eu: the blue shift occurred on the absorption edge, the mixing reduced the absorption of low energy photons in the crystal as a whole. At the same time, in the high-energy area, the absorption coefficient rises from 110000cm^-1 to 130000cm^-1, and doping with Eu increases the detection efficiency of the scintillation. This study can explain the increased detection efficiency of doped scintillation. The research in this paper provides the theoretical basis for the study of the mechanism of SrI₂ emission, and also provides the theoretical reference for the research of SrI₂ doping.