Coarse-grained simulation models can provide significant insight into the complex behavior of molecules in the condensed phase. In particular, "bottom-up" coarse-grained models retain chemical specificity by targeting the reproduction of properties from a higher-resolution reference model. However, these models are inherently limited by the molecular representation, set of interaction potentials, and parametrization method. These limitations often result in an inaccurate description of cross-correlations between coarse-grained degrees of freedom, complicating the stabilization of hierarchical structures in soft matter systems. Perhaps more troubling, reduced molecular friction and softer interaction potentials obscure the connection to the true dynamical properties of the system. In this work, we demonstrate how these two problems are interrelated and propose methodologies for characterizing and improving the dynamical properties generated by coarse-grained simulation models. A Markov-state-modeling framework is leveraged to systematically link microscopic interactions to the emergent long time scale kinetic processes. Our investigations identify structural-kinetic relationships that emerge from restricting certain features of the underlying free-energy landscape, and suggest a concerted approach for a balanced representation of system properties. As an alternative to expanding the set of molecular mechanics potentials typically employed to govern interactions between coarse-grained sites, we introduce a surface-hopping scheme that employs multiple coarse-grained force field surfaces for distinct intramolecular conformations of a molecule. Incorporating more surfaces leads systematically towards unimodal distributions along each coarse-grained degree of freedom within a given subsensemble, resulting in a more accurate description of both structure and dynamics.

Consistent representation of structural and dynamical properties from coarse-grained simulation models

2019 Fall National Meeting

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