Diffusion of helium in plutonium alloys

We have calculated the equilibrium volumes and total energies of delta Pu, Pu(3)Ga, and PuGa as a function of the occupation of the localized manifold. The energy is minimum with four 5f electrons localized in all cases, and the equilibrium volumes are close to the experimentally observed volumes. With this scheme, the delta phase is calculated to have an energy much closer to the energy of alpha Pu than with conventional calculations. We have also applied this scheme to the calculation of the tetragonal shear constant (C11-C12)/2 and find a that the lattice is stable against a tetragonal shear with a softened shear constant. Furthermore, the lowest energy crystal field state is a (non-magnetic) singlet, which would explain the lack of a moment in the delta phase