Vacancy clustering in zirconium: An atomic-scale study

The stability properties of vacancy clusters in hexagonal close-packed Zr—both cavities and dislocation loops—are investigated at the atomic scale, with a modeling approach based on density functional theory and empirical potentials. By considering the vacancy–vacancy interactions and the stability of small vacancy clusters, we establish how to build larger clusters. A study of extended vacancy clusters is then performed using continuous laws for defect energetics. Once validated with an empirical potential, these laws are parameterized with ab initio data. Our work shows that the easy formation of 〈a〉〈a〉 loops can be explained by their thermodynamic properties.