Eur. Phys. J. Special Topics 196, 3-13 (2011)
https://doi.org/10.1140/epjst/e2011-01413-4

Review

Theory of collective excitations in simple liquids

¹ Institut für Physik, Johannes Gutenberg-Universität Mainz, Staudinger Weg 7, 55099 Mainz, Germany
² Physik-Department E13, Technische Universität München, James-Franck-Strasse 1, 85747 Garching, Germany
³ European XFEL/DESY, Hamburg, Notkestr. 85, 22607 Hamburg, Germany

Received: 1 December 2010
Revised: 13 April 2011
Published online: 30 May 2011

Abstract

We present a parameter-free theory of the collective excitations in simple liquids such as liquid metals or rare gases. The theory is based on the mode-coupling theory (MCT), which has been previously applied successfully for explaining the liquid-to glass transition. The only input is the liquid structure factor. We achieve good agreement both for the liquid dispersion (maximum of the longitudinal current spectrum) and width (damping) with experimental findings. The time-dependent memory function predicted by MCT has a two-step exponential decay as previously found in computer simulations. Furthermore MCT predicts a scaling of the liquid dispersion with the effective hard-sphere diameter of the materials. This scaling is obeyed by the available experimental data.