Radiation Defects in Aluminum: MD Simulations of Collision Cascades in the Bulk of Material

Abstract

The molecular dynamics method has been used to simulate displacement cascades created by primary knock-on atoms (PKAs) with energies E_PKA= 5, 10, 15, and 20 keV in aluminum at temperatures T = 100, 300, and 600 K. A series of 24 cascades was simulated for each pair of the parameters (E_PKA, T) to ensure a representative sampling. The number of Frenkel pairs, the fraction of vacancies (ε_vac) and self-interstitial atoms (SIA) (ε_SIA) in point defect clusters, the average yield of vacancy (Y_vac) and SIA (Y_SIA) clusters per cascade, and the average relaxation time τ_c have been determined as a function of (E_PKA, T). It has been shown that displacement cascades of in aluminum decompose into several sub-cascades along PKA trajectory. Such a spatial structure of cascades is responsible for the absence of the dependence of the values of 〈ε_vac〉, 〈ε_SIA〉, 〈N_vac〉, 〈N_SIA〉, and τ_c on the energy of PKAs.