Atomistic calculation of point-defect diffusion anisotropy and irradiation growth in α-zirconium

The configuration and energetics of the mono-vacancy and self-interstitial of hcp zirconium, both in the ground state and the saddle-point configurations, are computed atomistically using the conjugate gradient method, from which the diffusion anisotropy difference (DAD) between the two types of defects is obtained. Based on this information, the growth rates of interstitial loops of different Burgers vectors in a zirconium foil irradiated in a high-voltage electron microscope and the stress-free in-reactor deformation rates in hcp zirconium are directly calculated. Experimental observations in both cases are shown to be well accounted for. The significance of the DAD effect is thus directly confirmed.