Simulation of Primary Radiation Damage in Nickel

Abstract

The process of radiation damage formation in collision cascades initiated by primary knock-on atoms (PKAs) with energy EPKA = 5, 10, 15, and 20 keV in nickel at temperatures T = 100, 300, 600, 900, and 1200 K was studied using the molecular dynamics method. To ensure the statistical validity of the results, a series of 24 cascades was modeled for each pair of (EPKA, T) parameters. The simulation results were analyzed to determine the number NFP of Frenkel pairs, fractions of vacancies σvac and interstitial atoms σSIA in clusters of point defects, average sizes of vacancy 〈Nvac〉 and interstitial 〈NSIA〉 clusters, and average numbers of vacancy 〈Yvac〉 and interstitial 〈YSIA〉 clusters produced in collision cascades as functions of the PKA energy and simulation temperature. It was found that the relation 〈NFP〉 = 2 ± 0.9 × $$E_{\text{PKA}}^{{1.1 \pm 0.1}}$$ holds true at all the examined values of (EPKA, T). The functional dependences of 〈σvac〉 and 〈σSIA〉 on EPKA were identical. The dependence of 〈σvac〉 follows that of 〈Yvac〉, while 〈σSIA〉 is governed by 〈NSIA〉 and the mobility of interstitials. The value of 〈Nvac〉 depends on the irradiation temperature and the thermal stability of vacancy clusters. These clusters are stable at T ≤ 300 K, and 〈Nvac〉 ∝ EPKA; at 600 ≤ T ≤ 900 K, 〈Nvac〉 ≈ 6 and 10, which corresponds to the sizes of regular stacking fault tetrahedra. The value of 〈YSIA〉 is proportional to 〈NFP〉 and, consequently, to EPKA in the entire range of PKA energies.