CALCULATION OF THE STRUCTURE FACTOR OF EXPANDED LIQUID CESIUM USING THE RANDOM-PHASE-APPROXIMATION WITH ONE-COMPONENT-PLASMA REFERENCE

We analyze the structure factor of expanded liquid cesium using the ra ndom phase approximation (RPA) with the classical one-component plasma (OCP) reference system. We extend the RPA by regarding the effective valence Z corresponding to the plasma parameter of the OCP reference as a free variable, which is fixed by approximately enforcing the vani shing of the pair correlation function g(r) at short distances. The ap plication of this RPA to the expanded Cs suggests that it works reason ably well up to 900-degrees-C similar to ORPA, which remains, however, somewhat more accurate in reproducing the observed structure factor S (q). An effect of the mean free path on the screening and the long-wav elength limit of the structure factor is also considered and is found to be small.