Comment on "collective dynamics in liquid lithium, sodium, and aluminum"

In a recent paper, Phys. Rev. E 67, 012201 (2003)] proposed a new interpretation of the collective dynamics in liquid metals and, in particular, of the relaxation mechanisms ruling density fluctuations propagation. At variance with both the predictions of the current literature and the results of recent inelastic x-ray scattering experiments, ST associate the quasielastic component of the S (Q,omega ) to the thermal relaxation, as it holds in ordinary adiabatic hydrodynamics valid for nonconductive liquids and in the Q-->0 limit. We show here that this interpretation leads to a nonphysical behavior of different thermodynamic and transport parameters.