Construction of dissipative particle dynamics models for complex fluids via the Mori-Zwanzig formulation

Area of Science:

• Soft Matter Physics
• Computational Chemistry
• Materials Science

Background:

• Coarse-graining (CG) methods reduce computational cost by representing groups of atoms as single particles.
• Existing CG methods often rely on empirical force fields, limiting their predictive accuracy.
• Bridging the gap between atomistic detail and mesoscopic behavior is crucial for simulating complex soft matter systems.

Purpose of the Study:

• To develop a general bottom-up coarse-graining procedure to construct mesoscopic force fields directly from microscopic dynamics.
• To evaluate the accuracy of dissipative particle dynamics (DPD) models informed by molecular dynamics (MD) simulations.
• To investigate the impact of different force field components on the static and dynamic properties of polymer melts.

Main Methods:

• A bottom-up coarse-graining strategy grouping bonded atoms into clusters.
• Molecular dynamics (MD) simulations of polymer melts to generate microscopic trajectories.
• Dissipative particle dynamics (DPD) simulations employing Mori-Zwanzig (MZ) projection for force field construction.
• Comparison of four DPD models with varying treatments of inter-cluster forces.

Main Results:

• DPD models with Mori-Zwanzig (MZ)-guided force fields significantly outperform standard DPD with empirical formulae in reproducing static and dynamic properties.
• Accurate reproduction of the velocity autocorrelation function and pair correlation function was achieved when rotational motion was considered.
• The developed framework demonstrates high fidelity in capturing the behavior of the underlying microscopic system.

Conclusions:

• The proposed bottom-up coarse-graining procedure provides a robust framework for deriving accurate mesoscopic force fields from atomistic simulations.
• MD-informed DPD models, particularly those accounting for rotational motion, offer superior predictive power for soft matter systems.
• This generalizable approach is applicable to various soft matter systems where clusters can be defined as CG particles.