Correspondence relation with respect to entanglement among different simulation models: comparison between bead-spring and bond fluctuation model

A novel index for comparing different simulation model polymers with respec t to entanglement is proposed. It is the number of elements, N-e* of ring p olymers whose average number of entanglement per molecule is unity; N-e* ca n be calculated with a small-scale computer simulation. We also proposed a method to equilibrate the entangled ring polymers. As an example we calcula ted N-e* with a molecular dynamics simulation using a bead-spring (BS) mode l which is equivalent to the model proposed by Kremer and Grest [J Chem Phy s 92 (1990) 5057], and with a Monte Carlo simulation using bond fluctuation (BF) model. We obtained N-e* = 82 +/- 1 for BF model with volume fraction phi = 0.43 and N-e* = 59 +/- 1 for BF model with phi = 0.5. By comparing wi th the recent result of our group, N-e = 89 for BF model with phi = 0.5, we can assume that N-e similar or equal to 1.5N(e)*. If this assumption holds for BS model, its N-e is estimated to be 120, which is 3.4 times greater t han the estimated value by Kremer and Grest. The origin of this difference is discussed. (C) 2000 Elsevier Science Ltd. All rights reserved.