ATHERMAL LATTICE POLYMERS - A COMPARISON OF RISM THEORY AND MONTE-CARLO SIMULATIONS

Polymer-RISM theory is applied to study athermal polymeric lattice flu ids. The intermolecular segmental distributions and the compressibilit y equation of state (EoS) have been obtained within the approach for t hree different intramolecular distribution functions, i.e., the random flight, the non reversal random walk, and an intramolecular distribut ion obtained from Monte Carlo simulations. Both the intermolecular seg mental distributions and the EoS are also compared to Monte Carlo simu lations. From the comparison to the simulations it is seen that the po lymer-RISM theory is well able to reproduce the intermolecular segment al distributions, but it underestimates the density dependence of the EoS: the EoS is worse than the classical Huggins EoS for the same mode l, and only for the computer simulated intramolecular distribution we find reasonable agreement between calculated and simulated EoS. The ab sence of liquidlike ordering effects in a lattice fluid allow us to sh ow to what extent the deviations are due to the incomplete incorporati on of excluded volume in the intramolecular distribution functions.