8th Liquid Matter Conference September 6-10, 2011 Wien, Austria ...

P4.12Fri 911:10-14:00Monte Carlo simulations of semiflexible polymer chains.Efficient sampling from compact to extended structuresChrister Elvingson, 1 Alexey Siretskiy, 1 Malek Khan, 1 and Pavel Vorontsov-Velyaminov 21 Uppsala university, Department of Physical chemistry, Ångströmlaboratoriet 751 05,Uppsala, Sweden2 St. Petersburg State University, St. Petersburg, Russian FederationMany macromolecules, both synthetic and biopolymers are semi-flexible, indicating a backbonestiffness. This will influence their structural features, and the characterization of the equilibriumproperties of these molecules is an ongoing effort. This is not least true for the compact structuresthis type of molecules can form in the presence of compacting agents. The original Metropolisalgorithm is not an efficient method for generating representative structures for compact polymers.In later years though there has been a large increase in methods for sampling configurations in awider size range, including e. g. entropic sampling [1] and the extended ensemble method [2]. Thecommon drawback of these methods is the necessity to manually introduce different parameters.With the introduction of the Wang-Landau algorithm [3], there was a method for ”automatic”adjustment of the simulation parameters. In particular we can now sample both very elongated andvery compact structures in a single computer experiment which was first applied to lattice polymers[4]. We have recently used similar ideas for a continuous model representing a semi-stiff polymerchain, showing the possibility to sample both extended and compact structures in a single computerexperiment. The sampling techniques used also significantly reduced the cpu-time, compared to e.g. pivot moves or crank-shaft moves. This sampling technique was then extended to investigatethe structure of polyampholytes, finding e. g. the most probable distribution of charges for variouschain compactions, and the probability distribution of the radius of gyration for various chargedistributions in a single simulation. [1] J. Lee, Phys. Rev. Lett. 71, 211 (1993). [2] A. Lyubartsev,et. al. , J. Chem. Phys. 96, 1776 (1992). [3] F. Wang and D. Landau, Phys. Rev. Lett. 64, 2050(2001). [4] T. Jain and J. de Pablo, J. Chem Phys. 116, 7238 (2002)12