First Principles Study of Phonon Modes in PuCoGa[sub 5] Superconductor

Abstract

By minimizing the total energy within the density-functional method we determined lattice parameters, atom positions, interatomic forces, and electronic structure of the new PuCoGa5 superconductor. The on-site Coulomb repulsion U and Hund’s exchange J lead to changes in the electronic structure, particularly near the Fermi energy, and to a better agreement between the calculated and experimental geometries. Using this ab initio input, the phonon dispersion relations are determined and classified by their symmetries. Phonon densities of states and the lattice heat capacity are discussed. Using individual contributions due to all optical modes at the point we estimate electron-phonon coupling 0.7 which does not suffice to explain the observed value of Tc and suggests that electronic interactions also play a role in the pairing mechanism.