TRIPLET CORRELATION-FUNCTIONS FOR HARD-SPHERES - COMPARISON OF DIFFERENT APPROACHES

We present numerical results of a comparison between several approxima tions for the determination of the triplet correlation functions of a simple liquid, which have been proposed during recent years; the syste m we have considered is a simple hard-sphere system. Two of the method s (one proposed by Barrat, Hansen, and Pastore [Phys. Rev. Lett. 58, 2 075 (1987); Mol. Phys, 63, 747 (1988)], and the other one based on a f ormal density expansion of the triplet distribution function) are pure ly numerical; the other two methods are based on a density-functional theory (reproducing both thermodynamics and pair structure of the Wert heim-Thiele description of hard spheres) and provide for this special system analytic expressions of the triplet direct correlation function in q space. If the triplet configurations are not too close (i.e., at most one direct contact between the spheres), we find good agreement between the different methods; this is quite remarkable since these ap proximations have completely different conceptual origins. If, however , the three particles form configurations with rather short interparti cle distances the differences in the results may become quite substant ial.