Theory-Informed Coarse-Grained Simulations of Polymer Liquids*

A number of coarse-grained models have been developed recently, such as IBI, Force Matching, and more. Starting from liquid state theory, in the Integral Equation Theory of Coarse-Graining (IECG), we formally investigate how structural, thermodynamic, and dynamical properties, as measured in a CG simulation, are affected by the coarse-graining procedure. CG Molecular Dynamics (MD) simulations validate the theoretical predictions by direct test with atomistic simulations.
The key issue is that because the CG potential is a free energy, it depends on the thermodynamic and molecular parameters of the atomistic system. This implies that a numerically optimized CG potential, as opposed to a formally derived one, can only apply to the system, at the thermodynamic conditions for which the potential has been optimized, i.e. the potential is not transferable to other conditions, nor is applicable to other molecular systems. The formally-derived, IECG approach affords instead transferable potentials, which predict structural and thermodynamic properties consistent with atomistic simulations. A number of thermodynamic and dynamical properties, instead, need to include analytical IECG corrections to reproduce the atomistic values.