Simulation of damage evolution and accumulation in vanadium

Abstract

Energetic atoms which have been knocked off their lattice sites by neutron or ion irradiation leave a trail of vacancies and interstitials in their wake. Most of these defects recombine with their opposites within their own collision cascade. Some fraction, however, escape to become freely migrating defects (FMD) in the bulk of the material. The interaction of FMD with the microstructure has long been linked to changes in the macroscopic properties of materials under irradiation. We calculate the fraction of FMD in pure vanadium for a wide range of temperatures and primary knock-on atom (PKA) energies. The collision cascade database is obtained from molecular dynamics (MD) simulations with an embedded atom method (EAM) potential. The actual FMD calculation is carried out by a kinetic Monte Carlo (kMC) code with a set of parameters extracted either from the experimental literature or from MD simulations. We take two different approaches to the problem and compare them. The first consists of an idealized simulation for single cascades. Annealing each cascade at different temperatures allows the mobile species to escape and account for FMD. The second analyzes bulk diffusion and damage.