Effect of doping on lattice dynamics and electron–phonon coupling of the actinides Ac–Th alloy

We have studied the electronic, lattice dynamical, and electron–phonon properties of the actinides ${Ac}_{1-x}$Th_x alloy within the framework of density functional perturbation theory. The self-consistent virtual crystal approximation is used for the alloy modeling, and spin–orbit coupling is included in the calculation of all relevant quantities. An overall decrease of the electron–phonon coupling (λ) by $53\%$ from Ac to Th was observed. However, its dependence on x shows a non-linear behavior. λ reduces just 6% from Ac to a Th content of $x=0.4$, then drops drastically (∼$47\%$) from there until $x=1$. The large decrease of λ for $x>0.4$ is due to the reduction of the density of states at the Fermi level ($N\left(E_F\right)$), combined with a general phonon hardening. On contrast, the behavior for $x⩽0.4$ is the result of a subtle balance between an enhancement of phase space and the above mentioned effects on $N\left(E_F\right)$ and the phonons. The phase-space enhancement is related to the appearance of Kohn anomalies, which fade away as the Th concentration increases. (paper)