Time-dependent current-density-functional theory for the metallic response of solids

We extend the formulation of time-dependent current-density-functional theory for the linear response properties of dielectric and semi-metallic solids [Kootstra et al., J. Chem. Phys. 112, 6517 (2000)] to treat metals as well. To achieve this, the Kohn-Sham response functions have to include both interband and intraband transitions with an accurate treatment of the Fermi surface in the Brillouin-zone integrations. The intraband contributions in particular have to be evaluated using a wave-vector-dependent description. To test the method we calculate the optical properties of the two noble metals Cu and Ag. The dielectric and energy loss functions are compared with experiments and with the classical Drude theory. In general we find a good agreement with the experiments for the calculated results obtained within the adiabatic local density approximation. In order to describe the Drude-like absorption below the interband onset and the sharp plasma feature in silver exchange-correlation, effects beyond the adiabatic local density approximation are needed, which may be included in a natural way in the present current-density-functional approach.