A MOLECULAR-DYNAMICS STUDY OF THE COLLECTIVE CORRELATION-FUNCTIONS OFA HARD-CORE FLUID WITH A YUKAWA TAIL

We present a molecular dynamics study of the collective correlation fu nctions of a hard-core system with an attractive Yukawa tail, for vari ous thermodynamic states in the fluid and liquid regions of the phase diagram. The results are compared with available information for hard spheres. The small-q behavior of the intermediate scattering functions indicates the propagation of sound waves, i.e., phononlike collective excitations, in the hard-core Yukawa system. The upper limit of q for these collective modes is practically independent of the thermodynami c state. The computed transverse current correlation functions show th at at liquid densities the hard-core Yukawa system is able to sustain shear wave propagation above a critical q; the upper limit of cl for s ound waves and the lower limit for shear waves nearly coincide. All of these features are qualitatively similar to those found for hard sphe res. However, there are significant quantitative differences, which re flect the influence of the attractive Yukawa tail on the dynamical beh avior of the system. (C) 1996 American Institute of Physics.