Title: A comparative study of coarse-graining methods for polymeric fluids: Mori-Zwanzig vs. iterative Boltzmann inversion vs. stochastic parametric optimization

Abstract

We construct effective coarse-grained (CG) models for polymeric fluids by employing two coarse-graining strategies. The first one is a forward-coarse-graining procedure by the Mori-Zwanzig (MZ) projection while the other one applies a reverse-coarse-graining procedure, such as the iterative Boltzmann inversion (IBI) and the stochastic parametric optimization (SPO). More specifically, we perform molecular dynamics (MD) simulations of star polymer melts to provide the atomistic fields to be coarse-grained. Each molecule of star polymer with internal degrees of freedom is coarsened into a single CG particle and the effective interactions between CG particles can be either evaluated directly from microscopic dynamics based on the MZ formalism, or obtained by the reverse methods, i.e., IBI and SPO. The forward procedure has no free parameters to tune and recovers the MD system faithfully. For the reverse procedure, we find that the parameters in CG models are not interchangeable. If the free parameters are properly selected, the reverse CG procedure also yields an effective potential. Furthermore, we explain how an aggressive coarse-graining procedure introduces many-body effect, which makes the pairwise potential invalid for the same system at densities away from the training point. From this work, general guidelines for coarse-graining of polymeric fluids can bemore » drawn.« less

Authors:

Li, Zhen  ^[1];

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Bian, Xin  ^[1];

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Yang, Xiu ^[2]; Karniadakis, George Em ^[1]

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+ Show Author Affiliations

1. Brown Univ., Providence, RI (United States)
2. Pacific Northwest National Lab. (PNNL), Richland, WA (United States)

Publication Date:

Mon Jul 25 00:00:00 EDT 2016

Research Org.:

Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States). Oak Ridge Leadership Computing Facility (OLCF); Pacific Northwest National Lab. (PNNL), Richland, WA (United States)

Sponsoring Org.:

USDOE Office of Science (SC), Basic Energy Sciences (BES). Scientific User Facilities Division

OSTI Identifier:

1356514

Alternate Identifier(s):

OSTI ID: 1272642

Report Number(s):

PNNL-SA-116567
Journal ID: ISSN 0021-9606; KJ0401000

Grant/Contract Number:  

AC05-76RL01830; W911NF-12-2-0023; AC02-06CH11357; AC05-00OR22725

Resource Type:

Journal Article: Accepted Manuscript

Journal Name:

Journal of Chemical Physics

Additional Journal Information:

Journal Volume: 145; Journal Issue: 4; Journal ID: ISSN 0021-9606

Publisher:

American Institute of Physics (AIP)

Country of Publication:

United States

Language:

English

Subject:

97 MATHEMATICS AND COMPUTING; Molecular dynamics; Polymers; Stochastic processes; Gyration radius; Many body problems; Newtonian mechanics; Nonequilibrium statistical mechanics; Static properties; Thermodynamic properties; Classical statistical mechanics