<i>Implementation of density functional theory for studies of tri-vacancies in unalloyed plutonium</i>

Studying vacancy clusters in fcc plutonium using density functional theory will provide further understanding in the stability of extended defects. We investigated tri-vacancies in unalloyed δ-plutonium using the generalized gradient approximation (GGA) exchange correlation functional using the projector augmented wave method in VASP. Ionic relaxation of a series of permutations of tri-vacancies in the δ-Pu matrix yielded only 8 unique ground state structures. Results indicate that the one of the most energetically stable structure is a Damask-Dienes-Weizer stacking fault tetrahedron (SFT), which has been predicted by MEAM calculations, while disperse vacancies are calculated to be thermodynamically unstable. A slightly lower energetic state than the SFT is calculated and is shown to be dependent on the magnetic configuration in the structure.