Effects of irradiation defects on the electronic structure and optical properties of LiI scintillator

As an important scintillation material, lithium iodide (LiI) crystal is commonly used in the field of neutron detection. Different irradiation defects, such as vacancy, antisite atom, interstitial atom, and transmutation elements (helium (He) and tritium (3H) ), are generated in the LiI crystal due to the neutron irradiation. To understand the effects of irradiation defects on the detection performance of the LiI scintillator, we investigated the effects of the irradiation defects on the electronic structure and optical properties of the LiI scintillator by using first principles calculation method in this paper. The results indicate that the self atom point defects and the H point defects reduce the band gap of the LiI scintillator, the reduced band gap can redshift the emission spectrum of the LiI scintillator and increase the visible light yield. The He point defects widen the band gap, which decreases the visible light yield. Therefore, the self atom point defects and the H point defects are helpful to improve the neutron detection efficiency of the LiI scintillator. In contrast, the He point defects reduce the neutron detection efficiency. Although the irradiation defects have some effects on the optical properties of the LiI scintillator, the effects are not significant. In conclusion, the irradiation defects can improve the neutron detection efficiency of the LiI scintillator except the He point defects.