Multiscale approach to equilibrating model polymer melts

TL;DR

This paper introduces a multiscale method for efficiently equilibrating polymer melts across different length scales, combining Monte Carlo annealing, Rouse dynamics, and force fields to achieve realistic configurations.

Contribution

The authors develop a simple, effective multiscale approach that progressively equilibrates polymer melts from large to small scales, improving simulation efficiency and accuracy.

Findings

Successfully equilibrated melts with 500 chains of 10,000 beads and 1,000 chains of 15,000 monomers.

Validated the method by analyzing the evolution of structural observables at multiple scales.

Demonstrated the approach's potential for extension to more complex polymer systems.

Abstract

We present an effective and simple multiscale method for equilibrating Kremer Grest model polymer melts of varying stiffness. In our approach, we progressively equilibrate the melt structure above the tube scale, inside the tube and finally at the monomeric scale. We make use of models designed to be computationally effective at each scale. Density fluctuations in the melt structure above the tube scale are minimized through a Monte Carlo simulated annealing of a lattice polymer model. Subsequently the melt structure below the tube scale is equilibrated via the Rouse dynamics of a force-capped Kremer-Grest model that allows chains to partially interpenetrate. Finally the Kremer-Grest force field is introduced to freeze the topological state and enforce correct monomer packing. We generate $15$ melts of $500$ chains of $10.000$ beads for varying chain stiffness as well as a number of melts with $1.000$ chains of $15.000$ monomers. To validate the equilibration process we study the time evolution of bulk, collective and single-chain observables at the monomeric, mesoscopic and macroscopic length scales. Extension of the present method to longer, branched or polydisperse chains and/or larger system sizes is straight forward.