A systematic investigation of electronic, lattice dynamical, and superconducting properties of the early actinides Ac, Th, and Pa within the framework of density functional perturbation theory is presented. Spin-orbit coupling is included self-consistently in the calculation of all relevant quantities. The largest coupling constant is obtained for Ac, which with $\lambda \approx 0.97$ is close to the strong coupling regime, and where a sizable superconducting transition temperature of 4–5 K is predicted. For Th and Pa, a reduced $\lambda \approx 0.5$ is found in accordance with the observed smaller $T_c$. By comparing with scalar-relativistic calculations we found that spin-orbit coupling results in a hardening of the phonon spectrum for all cases. Its influence on $\lambda$ is almost negligible for Ac and Pa. In contrast, for Th spin-orbit interaction invokes band splittings near the Fermi level, which reduces $\lambda$ by 21%.

• Received 3 December 2015
• Revised 22 February 2016

DOI:https://doi.org/10.1103/PhysRevB.93.104512