Simulation of displacement damage in CsPbBr₃ induced by neutron irradiation based on the Monte Carlo method

Cesium lead bromide (CsPbBr₃) is a fully inorganic halide perovskite material known for its excellent optoelectronic properties, offering significant advantages for applications in aerospace and nuclear fields. To evaluate its radiation hardness under neutron exposure, the transport process of 1-14 MeV neutrons in CsPbBr₃ was simulated using the Geant4 Monte Carlo toolkit. This study focuses on the primary damage characteristics, systematically analyzing the primary knock-on atom (PKA) spectrum and non-ionizing energy loss (NIEL). The simulation results indicate that most PKAs are distributed in the low-energy range. As the incident neutron energy increases, PKA types become more diverse, introducing transmutation products such as ^77-81Se, ¹³³Xe, ⁷⁶As, and ²⁰⁵Hg. Furthermore, a distinct anomaly is observed at lower neutron energies (∼3 MeV), where the displacement of Pb atoms exhibits a localized peak directly attributed to its prominent (n, n) elastic scattering resonance, although the overall macroscopic damage remains heavily dominated by the Br sublattice. Crucially, the calculated NIEL, number of displaced atoms (N_d), and displacements per atom (dpa) exhibit a non-monotonic dependence on incident neutron energy, initially increasing and then decreasing beyond ∼10 MeV. This trend is primarily driven by the transition from elastic to inelastic scattering dominance, coupled with increased ionizing energy partitioning at higher PKA energies. This paper provides fundamental data on the primary damage state of CsPbBr₃, establishing an essential source term basis for subsequent multiscale simulations of defect evolution.