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Orbital-free DFT study of the energetics of vacancy clustering and prismatic dislocation loop nucleation in aluminum

In the present work, we conduct large-scale orbital-free DFT calculations to study the energetics of vacancy clustering in aluminum from electronic structure calculations. The simulation domains considered in this study are as large as those containing a million atoms to accurately account for both the electronic structure and long-ranged elastic fields. Our results indicate that vacancy clustering is an energetically favorable mechanisms with positive binding energies for a range of vacancy clusters considered in the present study. In particular, the $19$ vacancy hexagonal cluster lying in $\{111\}$ 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 aluminum.