Lattice dynamics of metals from density-functional perturbation theory

The density-functional perturbation theory approach to lattice-dynamical calculations is extended to metallic systems. The smearing technique is used to deal with the Fermi surface and its variational formulation is restated. First-principles phonon dispersions of Al, Pb and of the transition metal Nb are in good agreement with available experimental data. In particular an accurate description of the anomalies observed in lead and niobium is obtained.