Determination of the interstitial electron density in liquid metals: Basic quantity to calculate the ion collective-mode velocity and related properties

Considering that various investigations identified a correlation between the interstitial electron density in crystalline metals and some ground-state properties, including the compressibility, we propose a procedure to estimate the interstitial electron density in liquid metals starting from the experimental static structure factor. From the calculated electron density, starting from the standard approximation, which describes a liquid metal as made up of a homogeneous classic ion plasma with Coulomb interaction and a homogeneous interacting electron gas, we determine the ion collective mode velocity. The so-derived collective mode velocity is compared to the experimental data and a coherent view in different metallic systems at the melting point is obtained. Some guess about the collective mode damping is also presented because of the connection to the local static fluctuations of the interstitial electron density.