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Bo Söderberg

Teaching staff

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Scaling and scale breaking in polyelectrolytes

Author

  • Carsten Peterson
  • Ola Sommelius
  • Bo Söderberg

Summary, in English

We consider the thermodynamics of a uniformly charged polyelectrolyte with harmonic bonds. For such a system there is at high temperatures an approximate scaling of global properties like the end-to-end distance and the interaction energy with the chain length divided by the temperature. This scaling is broken at low temperatures by the ultraviolet divergence of the Coulomb potential. By introducing a renormalization of the strength of the nearest-neighbor interaction the scaling is restored, making possible an efficient blocking method for emulating very large polyelectrolytes using small systems. The high temperature behavior is well reproduced by the analytical high-T expansions even for fairly low temperatures and system sizes. In addition, results from low-T expansions, where the coefficients have been computed numerically, are presented. These results approximate well the corresponding Monte Carlo results at realistic temperatures. A corresponding analysis of screened chains is performed. The situation here is complicated by the appearance of an additional parameter, the screening length. A window is found in parameter space, where scaling holds for conformational as well as thermodynamical properties. This window corresponds to situations where the range of the potential interpolates between the bond length and the size of the chain. This scaling behavior, which is verified by Monte Carlo results, is, for the end-to-end distance, consistent with Flory scaling. Also for the screened chain a blocking approach can be devised, that performs well for low temperatures, whereas the low-T expansion is inaccurate at realistic temperatures.

Department/s

  • Computational Biology and Biological Physics - Has been reorganised

Publishing year

1996

Language

English

Pages

5233-5241

Publication/Series

Journal of Chemical Physics

Volume

105

Issue

12

Document type

Journal article

Publisher

American Institute of Physics (AIP)

Status

Published

ISBN/ISSN/Other

  • ISSN: 0021-9606