Simulations of vacancy cluster behavior in δ-Pu

Using rates for vacancy diffusion in plutonium (Pu) found with parallel-replica dynamics, we develop a kinetic Monte Carlo (KMC) model of void growth and mobility. We compare and contrast the behavior of voids in Pu as predicted using vacancy mobilities from two different modified embedded atom method (MEAM) descriptions of Pu. We find that void behavior depends sensitively on the values used for vacancy mobility. In particular, we find that voids are very mobile in one model of Pu, but are essentially immobile in another, leading to very different void structures over time. This second model also predicts lifetimes for voids that are extremely long, and seemingly unphysical, suggesting that the first model is more representative of real Pu.