One of the most debated and still unsettled subjects in the field of fluids physics is the microscopic mechanisms responsible for the propagation and the attenuation of density fluctuations in liquid metals. Understanding these mechanisms would allow to disentangle disorder-driven effects (common to a wider variety of systems from glasses to undercooled liquids) from those strictly connected to the presence of an electron gas. High resolution and small-angle inelastic neutron scattering measurements on a large class of liquid metals are presented in order to clarify the driving role of the electron density in the propagation and decay of collective excitations. We show that the coherent dynamics and in particular the anomalous propagation velocity and the damping of the collective excitations can be related quantitatively to the screening of the ionic potential by the electron gas. Instead, the self-diffusive behavior and the cage-like effects are analogous to that of other dense fluids. The interpretations of these measurements are further supported by large scale Molecular Dynamics Simulations based on a many-body effective potential exploiting the two component (electron and ions) model for the liquid metal.
CRS-SOFT c/o Institut Laue Langevin, Grenoble.