Electronic and vibrational properties of Pu3Ga: A theoretical explanation for the phonon softening observed in Pu-Ga alloys

By using the density functional theory plus U (DFT+U) method and taking spin-orbit coupling into account, we investigate the electronic and phonon properties of Pu3Ga. Most interestingly, we find that there is a significant phonon softening in the transverse acoustic branch at the L point in the Brillouin zone. Via bond strength analysis, we reveal that the nearest-neighboring bond strengths in the face-centered-cubic lattice are weaker around Ga atoms, which is responsible for the observed phonon softening.