Grande conférence iLM

Friday 10 June 2011 à 14h00.

Fingerprints of order and disorder in the microscopic dynamics of simple liquids

Valentina Giordano



Invité(e) par
PIERRE-LOUIS OLIVIER

présentera en 1 heure :

''It is largely accepted that liquids present a local order usually corresponding to that of the solid phase at the same density. It is less clear to what extent the existence of such a short-range order affects the properties of the liquid, and more in detail its microscopic dynamics. In particular, high-frequency collective excitations reminiscent of phonons in solids exist as well in liquids. They are however traditionally discussed in terms of relaxation processes characteristic of the liquid phase. I will present in this talk the current understanding of the roles played by order and disorder in the microscopic dynamics of simple liquids, as we have recently achieved by means of a detailed investigation and quantitative comparison between the microscopic dynamics of liquid and polycrystalline sodium. I'll show that liquid sodium exhibits acoustic excitations of both longitudinal and transverse polarization at frequencies strictly related to those of the corresponding crystal. The only relevant difference between the liquid and the polycrystal appears in an additional, disorder-induced broadening of the excitations. I will also show that the same picture holds as well for a non-simple liquid as liquid gallium. This opens then new possibilities for the investigation of liquids, revealing a close and well specific relation between local order and dynamics in disordered systems.''