Threshold displacement energies and neutron-induced displacement-per-atom response of CsPbBr3 from molecular dynamics and Monte Carlo simulations
CsPbBr3 is a promising halide perovskite for ionising radiation detection, but its displacement damage under fast neutron irradiation is not yet well understood. This work combines molecular dynamics simulations with Geant4 Monte Carlo calculations to study threshold displacement energies and neutron induced DPA in CsPbBr3. An ICSD based orthorhombic structure was used for site specific threshold energy calculations. The interatomic potential used Buckingham ZBL short range terms and long range Coulomb interactions, and was checked by structural relaxation, finite temperature equilibration and elastic constants against DFT and experimental data. Threshold displacement energies were calculated for Cs, Pb, apical Br and equatorial Br at 100, 200 and 300 K, using 100 recoil directions and three random seeds for each direction. The results show strong site and direction dependence. Pb has the highest average threshold displacement energy, while the two Br sites show different displacement responses. The MD based threshold energies were then used in Geant4 recoil damage calculations for 2.45 MeV and 14.1 MeV fusion relevant neutrons. Species resolved recoil spectra were obtained for Cs, Pb and Br. DPA values were calculated using a Lindhard damage energy partition and an NRT displacement model. For a 1 cm3 CsPbBr3 detector volume, the DPA per incident neutron is 9.056 x 10 to the minus 22 at 2.45 MeV and 1.248 x 10 to the minus 21 at 14.1 MeV. These results provide atomistic threshold displacement data and neutron damage estimates for evaluating the radiation tolerance of CsPbBr3 neutron detectors.