The structure and thermodynamic properties of the freely jointed linear chain fluid with monomers interecting by the Lennard-Jones potential are studied using the polymer Percus-Yevick (PPY) ideal chain approximation. The theory is based on the Wertheim's multidensity integral-equation theory for associating fluids, appropriately modified to describe the polymer fluids. In the case of the chain system composed of 4, 8 and 16 monomeric units the PPY ideal chain approximation is found to yield good agreement with corresponding computer simulation results for the internal energy at the entire range of the density and temperature studied. For the longer chains composed of 50 and 100 segments the agreement becomes slightly worse, especially at low values of the density. Predictions of the theory for the structure properties are less satisfactory, i.e. theoretical results for the intermolecular everage site-site distribution function of 16-mer fluid is only in semiquantitative agreement with Monte Carlo simulation results. It is expected, that the thery will be more accurate in predicting overall everage distribution functions and for the fluid of shorter chain length.Comments: Figs. 8, Refs. 14, Tabs. 0.
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