Core polarization and the dielectric response of simple metals

The effect of core polarization on the dielectric properties of simple metals with free-electron-like conduction bands is investigated within the random-phase approximation. The charge fluctuations of both the core and valence electrons are treated on an equal footing. The screening fields due to the core dipole moments contribute a term to the frequency-dependent dielectric function of the Clausius-Mossotti form. An important aspect of the present approach is the precise definition of the core polarizability, which is characteristic of an ion imbedded in a metal. The use of the dielectric function in a determination of the plasma frequency is found to yield excellent results in the case of Cd, In, and Sn. Results for the optical conductivity and electron-energy-loss function are also found to be in qualitative agreement with experiment for a variety of metals. Discrepancies in the plasma frequency of Al suggest that a more detailed treatment of band-structure effects may be required to obtain quantitative agreement with experiment for some metals.