Toward Transferable Coarse-Grained Potentials for Poly-Aromatic Hydrocarbons: A Force Matching Approach

M Tripathy and U Agarwal and PBS Kumar, MACROMOLECULAR THEORY AND SIMULATIONS, 28, 1800040 (2019).

DOI: 10.1002/mats.201800040

Poly-aromatic hydrocarbons (PAHs) have been the subject of numerous experimental investigations for their multitude of existence, from particulate soot to the vast cosmos. Given the structural peculiarity of PAHs, where aromatic moieties serve as the basic building blocks, a generalized coarse-grained (CG) description befits and holds immense potential to investigate large-scale PAH systems and their derivatives via CG simulation. Toward this, a minimal CG mapping scheme is proposed where a set of PAHs are modeled as planar molecules made up of oblate ellipsoids, which interact via uniaxial Gay-Berne (GB) potential. A force-based systematic coarse-graining approach is followed to extract the CG force field parameters. The resulting GB parameters are found to be either comparable or show definite trends as a function of molecular size. CG simulation is shown to retain the qualitative structural features of the underlying atomistic systems with multi-fold decrease in computational cost. Accelerated equilibration of atomistic systems is shown to be achievable by MC simulations of CG systems followed by back- mapping, where the atomistic structure is exactly reproduced.

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