The evolution of radiation-induced point defects near symmetrical tilt Σ5 (3 1 0) 〈0 0 1〉 grain boundary in Ga stabilised δ-Pu: A molecular dynamics study

Abstract

Molecular dynamics (MD) simulations were performed to investigate the evolution of radiation-induced point defects affected by the symmetrical tilt Σ5 (310) 〈001〉 grain boundary (GB) in Ga stabilised δ-Pu. From the perspective of formation energy, the formation energy of vacancies had no prominent change in the whole region, but it was lower than the formation energy of interstitial atoms. The formation energy of interstitial atoms near GB was lower than that in the bulk. On the other hand, the average formation energy of interstitial Pu atoms was greater than that of interstitial Ga atoms. Furthermore, by comparing the evolution of radiation-induced point defects when primary knock-on atom (PKA) was located at −25 Å and 25 Å far from the GB, respectively, and analyzing the tendency of the number of remaining defects with the distance between PKA and GB changing, it could be found that interstitial atoms were more easily trapped in Σ5 (310) 〈001〉 GB than vacancies for Pu-Ga alloy. Simultaneously, the influence of temperature on the number of point defects near GB was taken into consideration, and the results displayed that the number of residual point defects in Pu-Ga alloy with Σ5 (310) 〈001〉 GB showed a decreasing trend with temperature increasing because temperature had an effect on the diffusion of point defects. Remaining interstitial atoms rather than remaining vacancies, moreover, are more severely affected by temperature, for interstitial atoms were more easily absorbed by GB.