Thermodynamic Perturbation Approach to Freezing of the Classical One-Component Plasma

Abstract

Systematic investigations are made of the thermodynamic perturbationapproach to freezing, which has proved successful for systemsinteracting through soft-core or long-ranged potentials. The classicalone-component plasma (OCP) is taken as the extreme case of suchsystems and the investigations focus on the reference systems employedin this approach and on the approximation schemes used to treat thatsystem. It is confirmed that good results are obtained for thefreezing properties of the OCP if a system with repulsive, short-ranged potential is properly chosen as the reference system, andboth this system and the remaining part due to the long-rangeinteraction are separately treated by the modified weighted-densityapproximation (MWDA) using accurate input data. However, if we adoptthe hard spheres as the reference system in this approach and useeither the MWDA or the generalized effective-liquid approximation(GELA) for this system, we cannot get similar results unless we usethe input data in the Percus-Yevick (PY) approximation rather than thevirtually “ exact'' ones. This unfavorable result throwsserious doubt on the usefulness of the hard spheres as the referencesystem.