ANALYTICAL TREATMENT OF THE FUSED HARD-SPHERE CHAIN MODEL - 0.5-LESS-THAN-L-LESS-THAN-1

Multidensity integral equation theory for a model of an associating fl uid forming freely jointed fused hard-sphere chain, is presented. Our approach is based on the Wertheim's polymer Percus-Yevick (PPY) theory supplemented by the ideal chain approximation and can be regarded as an extension of the PPY theory for tangent hard-sphere fluids proposed by Chang and Sandler (J. Chem. Phys. 102, 1995, 437). The radial dist ribution function and the structure factor are calculated for the diff erent model parameters. We compare the resulting predictions for the i ntermolecular distribution function with the Monte Carlo simulation re sults for the fused diatomic system. It is found that the accuracy of the prediction of the structure of such system is realiable in a rathe r wide range of density. It is shown that structure factor exhibits a peculiarity (so-called pre-peak) at small wave numbers, connected with the formation of relatively large molecular aggregates. The dependenc e of the pre-peak magnitude on the degree of penetrability is investig ated and discussed.