The influence of PKA direction on displacement cascade evolution

摘要

An extensive database of atomic displacement cascades in iron has been developed using molecular dynamic simulations. More than 300 cascades have been completed at 100K at energies between 100 eV and 100 keV, with fewer simulations at 600 and 900K. A systematic evaluation of the database has revealed an unexpected influence of PKA direction in low energy simulations. For primary knockon (PKA) directions that lie in the close-packed {110} planes, the cascade tends to be constrained to develop in only two dimensions. This planar "channeling" leads to much higher point defect survival than when a random high-index PKA direction is used to initiate the cascade. For example, the average number of stable Frenkel pair produced in 300 eV cascades is about 2.1 for cascades initiated with a [135] PKA, and 3.2 for [114] cascades. Some influence of this PKA direction effect was observed for energies up to 2 keV. The interstitial clustering behavior also appears to be affected in cascades with high defect survival.