MONTE-CARLO SIMULATION OF LENNARD-JONES CHAINS

Thermodynamical properties of ''infinitely stiff'' freely jointed Lennard-Jones chains are obtained through Monte Carlo simulation technique in the canonical (NVT) ensemble. A force-bias sampling scheme is used in the simulation. The compressibility factor, energy, and constant-volume heat capacity of 8-, 16-, and 32-mer Lennard-Jones chains over wide ranges of densities and temperatures are obtained. It is known that the virial pressure of infinitely stiff freely jointed Lennard-Jones chains depends on two- and three-body correlations between segments. We determine, for the first time, these two contributions to the viral pressure of Lennard-Jones chains, and found that their relative magnitudes are comparable with each other. While the three-body term remains positive for all temperatures and densities examined, the two-body term adopts negative values at low temperatures and densities and positive values at high temperatures and densities. Our simulation results reveal the importance of three-body intrachain correlations that arise from chain connectivity and provide a quantitative basis for the assessment and development of theories for chain fluids.