Orbital-free density functional theory study of the energetics of vacancy clustering and prismatic dislocation loop nucleation in aluminium

In the present work, we conduct large-scale orbital-free density functional theory calculations to study the energetics of vacancy clustering in aluminium from electronic structure calculations by accurately accounting for both the electronic structure and long-ranged elastic fields. Our results show positive binding energies for a range of vacancy clusters considered. However, the binding energies for the various quad-vacancy clusters considered in this study are vastly different, and only some of these clusters are found to be stable with respect to dissociation into divacancies. This suggests that, while vacancy clustering is an energetically feasible mechanism, this happens preferentially through the formation of certain vacancy clusters. Among the vacancy clusters considered in this study, the 19 vacancy hexagonal cluster lying in {11} plane has a very large binding energy with the relaxed atomic structure representative of a prismatic dislocation loop. This suggests that vacancy prismatic loops as small as those formed from 19 vacancies are stable, thus providing insights into the nucleation sizes of these defects in aluminium.