1ST-PRINCIPLES EVALUATION OF DYNAMIC-RESPONSE AND PLASMON DISPERSION IN METALS

We report an ab initio evaluation of the dynamical density-response fu nction for real Al and Na. The method we employ is a generalization of the Dalgarno-Lewis scheme of perturbation theory to systems with a co ntinuous spectrum and to dynamical problems. The crystal lattice is fo und to lower the plasmon frequency of Al for large wave vectors by as much as 4 eV. For this metal, agreement with experiment is excellent i n the time-dependent local-density approximation for exchange correlat ion. The ''anomalous'' dispersion observed for Na for large wave vecto rs is assigned to subtler exchange-correlation effects.