Radiation damage buildup and basal vacancy cluster formation in hcp zirconium: A molecular dynamics study

Abstract

Irradiation-induced damage buildup in alpha zirconium is investigated using Molecular Dynamics (MD) simulations of cascade overlap. It is found that the damage accumulates very quickly at low dose and then reaches a steady level after around 0.1 dpa. We also observe that high temperature is able to significantly decrease the steady damage while recoil energy exhibits a small effect on the defect accumulation. Most importantly, we find that cascade overlap in hcp Zr naturally creates basal vacancy clusters, which have been seldom observed in simulations of single cascades. Based on our calculations of binding energies of defect clusters and simulations of single 50 keV cascades in strained crystals, we show that the local strain induced by the defect debris in the heavily-irradiated crystal is a possible mechanism for the formation of basal vacancy clusters in hcp Zr. Finally the reliability of the used potential for investigating strain effects is discussed based on calculations of stacking fault energy (SFE) under strains.