Coarse-Graining Simulation Approaches for Polymer Melts: Range of Potential and Computational Efficiency

TL;DR

This paper evaluates the integral equation coarse-graining (IECG) method for polymer melts, analyzing how different parameters influence computational efficiency and demonstrating significant speed-ups over atomistic simulations.

Contribution

It provides a comprehensive analysis of the IECG approach, including optimal parameters for efficiency and parallel scalability, for various coarse-graining levels in polymer melt simulations.

Findings

Maximum efficiency achieved with highest CG level (soft spheres)

Speed-up of about 10^6 to 10^8 times compared to atomistic models

Parallel scalability is optimal with a large number of processors

Abstract

The integral equation coarse-graining (IECG) approach is a promising high-level coarse-graining (CG) method for polymer melts, with variable resolution from soft spheres to multi CG sites, which preserves the structural and thermodynamical consistencies with the related atomistic simulations. When compared to the atomistic description, the procedure of coarse-graining results in smoother free energy surfaces, longer-ranged potentials, a decrease in the number of interaction sites for a given polymer, and more. Because these changes have competing effects on the computational efficiency of the CG model, care needs to be taken when studying the effect of coarse-graining on the computational speed-up in CG molecular dynamics simulations. For instance, treatment of long-range CG interactions requires the selection of cutoff distances that include the attractive part of the effective CG potential and force. In particular, we show how the complex nature of the range and curvature of the effective CG potential, the selection of a suitable CG timestep, the choice of the cutoff distance, the molecular dynamics algorithms, and the smoothness of the CG free energy surface affect the efficiency of IECG simulations. By direct comparison with the atomistic simulations of relatively short chain polymer melts, we find that the overall computational efficiency is highest for the highest level of CG (soft spheres), with an overall improvement of the computational efficiency being about $10^6-10^8$ for various CG levels/resolutions. Therefore, the IECG method can have important applications in molecular dynamics simulations of polymeric systems. Finally, making use of the standard spatial decomposition algorithm, the parallel scalability of the IECG simulations for various levels of CG is presented. Optimal parallel scaling is observed for a reasonably large number of processors.