Equations of state of freely jointed hard-sphere chain fluids: Numerical results

We continue our series of studies in which the equations of state (EOS) are derived based on the product-reactant Ornstein-Zernike approach (PROZA) an d first-order thermodynamic perturbation theory (TPT1). These include two c ompressibility EOS, two virial EOS, and one TPT1 EOS (TPT1-D) that uses the structural information of the dimer fluid as input. In this study, we carr y out the numerical implementation for these five EOS and compare their num erical results as well as those obtained from Attard's EOS and GF-D (genera lized Flory-dimer) EOS with computer simulation results for the correspondi ng chain models over a wide range of densities and chain length. The compar ison shows that our compressibility EOS, GF-D, and TPT1-D are in quantitati ve agreement with simulation results, and TPT1-D is the best among various EOS according to its average absolute deviation (AAD). On the basis of a co mparison of limited data, our virial EOS appears to be superior to the pred ictions of Attard's approximate virial EOS and the approximate virial EOS d erived by Schweizer and Curro in the context of the PRISM approach; all of them are only qualitatively accurate. The degree of accuracy predicted by o ur compressibility EOS is comparable to that of GF-D EOS, and both of them overestimate the compressibility factor at low densities and underestimate it at high densities. The compressibility factor of a polydisperse homonucl ear chain system is also investigated in this work via our compressibility EOS; the numerical results are identical to those of a monodisperse system with the same chain length. (C) 1999 American Institute of Physics. [S0021- 9606(99)50810-6].