Thermodynamic, alloying and defect properties of plutonium: Density-functional calculations

We show that thermodynamic properties of Pu metal as well as those of Pu(1−x)Mx (M = Al, Ga, In) compounds are poorly described by traditional DFT but rather well modeled when including magnetic interactions. The cluster variation method is used to emphasize that the presence of Ga atoms in the δ-Pu phase leads to an important chemical short-range order which stabilizes this phase as a function of temperature and composition. Our results indicate also that Ga atoms introduce local strain fields in δ phase which relax with increasing distance from the Ga atoms. Finally we show that local relaxations are also essential to predict correct vacancy formation and migration energies in this phase.