General Equilibration of Macromolecular Systems by Kuhn-Scale Mapping and Dynamic Backmapping

We present a General Approach for Macromolecular Equilibration via Restrained Simulations (GAMERS). Equilibrating polymer systems is a challenging endeavor, particularly as relaxation times often exceed timescales accessible by atomistic molecular dynamics. The use of coarse-grained (CG) models followed by backmapping can mitigate such issues but typically requires substantial technical effort to obtain chemistry-specific CG models. By contrast, GAMERS equilibrates phenomenological models, establishes system-specific mappings via a polymer-physics oriented isomorphism, and then guides atomistic segments to target positions with time-dependent biasing forces. We demonstrate GAMERS by using Kremer-Grest models to equilibrate four chemically distinct polymers: polyethylene oxide, cis-polybutadiene, bisphenol A polycarbonate, and atactic polystyrene. The method rapidly converges to correct densities and reproduces expected chain statistics at and above the Kuhn length. Comparison of mechanical properties across initialization strategies reveals substantial differences in tensile response, underscoring the importance of proper equilibration. This positions GAMERS as an effective option to equilibrate polymer systems with modest resources, while avoiding bottom-up CG model development and preserving the benefits of hierarchical equilibration.