Electronic and vibrational properties of Pu3 M (M=Al, Ga, In, and Tl): A first-principles study ELECTRONIC and VIBRATIONAL PROPERTIES of ... LI, YANG, ZHENG, WANG, and ZHANG

We investigated the structural, electronic, magnetic, and phonon properties of Pu3M, where M = Al, Ga, In, and Tl, using first-principles calculations with the spin-orbit coupling taken into consideration. All four compounds are found to contain transverse phonons along [011] and [111] that remarkably soften at the boundaries of the first Brillouin zone, corresponding to the M and R points. Through detailed analyses of the vibrational modes and bond strengths, we reveal that all four types of M atoms have softer bonding with neighboring Pu than Pu-Pu bond, which accounts for the phonon softening and may shed light on the δ-stabilization of Pu by trivalent metal doping. In addition, we find that, due to the missing p-d hybridization, Pu3Al behaves quite differently from the other three Pu3M compounds. For example, Pu3Al has an unexpected equilibrium volume and high-frequency disentangled optical branches of phonons.