Molecular dynamics simulation of defect production in Fe due to irradiation

Molecular dynamics simulations were performed to investigate displacement cascades in Fe as a function of primary knock-on atom (PKA) energy. The statistics of defect production due to displacement cascades was focused in this study, where 1000 cases were simulated for individual PKA energies. It was found in our simulations that the simulated probability density function of the number of athermal point defects produced by the displacement cascade exhibits approximately a normal distribution. For PKA energies below 100 eV, the average number of surviving point defects is in proportion to PKA energy with a constant standard deviation. On the other hand, for higher energies, the average and the standard deviation individually show a power dependence on PKA energy. The PKA energy dependences of the average number of surviving point defects are consistent with those of the NRT and Bacon models for lower and higher PKA energies, respectively. Statistical characteristics of displacement cascades will help to describe the changes in the microstructure and mechanical properties of materials under irradiation.