COLLECTIVE DENSITY EXCITATIONS IN LIQUID CESIUM

Using the Mori-Zwanzig memory function formalism with an hyperbolic se cant form for the second order memory function, we calculate the dynam ical structure factor of liquid Cesium at its melting point. The two p arameters appearing in the memory function are determined from the sum rules of the density-density correlation function. The required input s are an interatomic potential and the corresponding pair correlation function. The calculations are performed with the Price-Singwi-Tosi po tential for liquid metals and the predicted results for S(q, omega) sh ow collective density excitations for wave numbers q less than or equa l to 1 Angstrom(-1), in agreement with experimental results.