While coarse-graining and multi-scale approaches are rapidly becoming an important tool for simulations of large complex molecular systems, many numerical optimization approaches suffer from a lack of thermodynamic consistency between various levels of representation. On a theoretical level, it is not well-understood how small correlations in the long-range structure propagate through the coarse-graining procedure into the effective potential and lead to incorrect thermodynamics. Taking an alternative approach to numerical optimization procedures, we have developed an analytical coarse-graining method where a group of atoms on a polymer chain are represented by a variable numbers of soft interacting �effective� sites. The approach is based in liquid-state theory, allowing us to address questions of thermodynamic consistency from a solid theoretical framework. This talk will address the issues of transferability and representability for highly coarse-grained models of polymer melts. Importantly, we find that the long tail of the potential scales non-trivially with the number of underlying monomers represented by a single effective site as N1/4 [1]. The long-range shape of the potential is shown to be essential for obtaining the correct virial pressure from simulations, despite having little effect on the center of mass pair correlation function. Finally, we will address the implications of coarse-graining on the entropy and potential energies of the system, which must take into account the smoothed energy landscape and the reduced degrees of freedom inherent to coarse-grained models.  1. A. Clark, J. McCarty, I. Y. Lyubimov, M. G. Guenza, Phys. Rev. Lett. 109, 168301-5 (2012).

Lessons from analytical coarse-graining: Representability, thermodynamic consistency, and long range correlations

246th National Meeting (2013)

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