Van der Waals forces in metals

An analysis is made of the dispersion (Van der Waals) interaction between the ions in a metal. The role of the dielectric function ε(k, ω) of the electron gas in screening polarization fluctuations of the ions is studied, and it is established that in Van der Waals interaction there will be terms which are analogs of the Thomas-Fermi screening term and the Friedel oscillation term occurring in the static interaction between ions. It is shown that reasonable estimates of the Van der Waals energy can be made by ignoring the spatial dispersion aspect of ε(k, ω), using a local approximation based on the bulk-plasmon term only.