Anisotropic diffusion of radiation-induced self-interstitial clusters in HCP zirconium: a molecular dynamics and rate-theory assessment

TL;DR

This study investigates the anisotropic diffusion behavior of radiation-induced self-interstitial atom clusters in zirconium using molecular dynamics simulations and rate-theory modeling, revealing differences between cascade-induced and equilibrium clusters.

Contribution

It provides new insights into the anisotropic diffusion of self-interstitial clusters in zirconium and estimates parameters for rate-theory models based on MD simulations.

Findings

Cascade-induced clusters are more anisotropic than equilibrium clusters.

Both 1D and 2D diffusing clusters are observed.

Predicted growth strains align with experimental data but depend on interatomic potentials.

Abstract

Under irradiation, Zr and Zr alloys undergo growth in the absence of applied stress. This phenomenon is thought to be associated with the anisotropy of diffusion of either or both radiation-induced point defects and defect clusters. In this work, molecular dynamic simulations are used to study the anisotropy of diffusion of self-interstitial atom clusters. Both near-equilibrium clusters generated by aggregation of self-interstitial atoms and cascade-induced clusters were considered. The cascade-induced clusters display more anisotropy than their counterparts produced by aggregation. In addition to 1-dimensional diffusing clusters, 2-dimensional diffusing clusters were observed. Using our molecular dynamic simulations, the input parameters for the "self-interstitial atom cluster bias" rate-theory model were estimated. The radiation-induced growth strains predicted using this model are largely consistent with experiments, but are highly sensitive to the choice of interatomic interaction potential.