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Dynamical properties of the slithering-snake algorithm: A numerical test of the activated-reptation hypothesis

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http://pubman.mpdl.mpg.de/cone/persons/resource/persons48356

Luijten,  E.
MPI for Polymer Research, Max Planck Society;

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Citation

Mattioni, L., Wittmer, J. P., Baschnagel, J., Barrat, J. L., & Luijten, E. (2003). Dynamical properties of the slithering-snake algorithm: A numerical test of the activated-reptation hypothesis. The European Physical Journal E, 10(4), 369-385.


Cite as: http://hdl.handle.net/11858/00-001M-0000-000F-6317-B
Abstract
Correlations in the motion of reptating polymers in a melt are investigated by means of Monte Carlo simulations of the three-dimensional slithering-snake version of the bond-fluctuation model. Surprisingly, the slithering-snake dynamics becomes inconsistent with classical reptation predictions at high chain overlap (created either by chain length N or by the volume fraction φ of occupied lattice sites), where the relaxation times increase much faster than expected. This is due to the anomalous curvilinear diffusion in a finite time window whose upper bound τ+(N) is set by the density of chain ends φ/N. Density fluctuations created by passing chain ends allow a reference polymer to break out of the local cage of immobile obstacles created by neighboring chains. The dynamics of dense solutions of “snakes” at t«τ+ is identical to that of a benchmark system where all chains but one are frozen. We demonstrate that the subdiffusive dynamical regime is caused by the slow creeping of a chain out of its correlation hole. Our results are in good qualitative agreement with the activated-reptation scheme proposed recently by Semenov and Rubinstein (Eur. Phys. J. B, 1 (1998) 87). Additionally, we briefly comment on the relevance of local relaxation pathways within a slithering-snake scheme. Our preliminary results suggest that a judicious choice of the ratio of local to slithering-snake moves is crucial to equilibrate a melt of long chains efficiently.