pith. sign in

arxiv: 2512.18272 · v1 · pith:E47CE5YBnew · submitted 2025-12-20 · 🧮 math.NA · cond-mat.soft· cs.NA

Hybrid multiscale method for polymer melts: analysis and simulations

Pith reviewed 2026-05-25 07:51 UTC · model grok-4.3

classification 🧮 math.NA cond-mat.softcs.NA
keywords hybrid multiscale methodpolymer meltsCahn-Hilliard-Navier-StokesIrving-Kirkwood formulaphase segregationfinite element methodring polymersmolecular dynamics
0
0 comments X

The pith

A hybrid method extracts stress tensors from molecular dynamics to drive a Cahn-Hilliard-Navier-Stokes model of ring polymer melts under flow.

A machine-rendered reading of the paper's core claim, the machinery that carries it, and where it could break.

The paper constructs a hybrid multiscale framework for dense melts of flexible and semiflexible ring polymers near walls. Molecular dynamics trajectories supply an averaged stress tensor via the Irving-Kirkwood formula, which is then inserted into a macroscopic Cahn-Hilliard-Navier-Stokes system equipped with dynamic and no-slip boundary conditions. Finite-element discretizations of the macroscopic system are shown to be solvable and energy-stable, and the model reproduces observed phase segregation once effective attractive forces are added.

Core claim

Phase segregation under flow between flexible and semiflexible rings, as observed in microscopic simulations, can be replicated in the macroscopic Cahn-Hilliard-Navier-Stokes model by introducing effective attractive forces, with the stress tensor supplied directly by the Irving-Kirkwood formula applied to molecular-dynamics data.

What carries the argument

The hybrid coupling that inserts the Irving-Kirkwood stress tensor computed from molecular-dynamics trajectories into the Cahn-Hilliard-Navier-Stokes equations.

If this is right

  • The finite-element scheme for the coupled system admits solutions and satisfies an energy stability bound.
  • Phase segregation observed at the particle level can be recovered at the continuum level once effective attractive forces are introduced.
  • The approach supplies a computationally cheaper route to large-scale flow simulations of ring-polymer mixtures near walls.

Where Pith is reading between the lines

These are editorial extensions of the paper, not claims the author makes directly.

  • The same stress-transfer procedure could be tested on linear or branched polymers to check whether the effective-force correction remains sufficient.
  • Varying the wall boundary conditions in the macroscopic model would reveal how sensitive segregation patterns are to the dynamic versus no-slip choice.
  • If the Irving-Kirkwood averaging length scale is changed, the macroscopic segregation threshold should shift in a predictable way that can be checked against new molecular-dynamics runs.

Load-bearing premise

The stress tensor obtained from molecular-dynamics trajectories via the Irving-Kirkwood formula can be directly substituted into the continuum Cahn-Hilliard-Navier-Stokes system.

What would settle it

A numerical experiment in which the macroscopic model without effective attractive forces produces no phase segregation while the underlying molecular-dynamics trajectories do.

Figures

Figures reproduced from arXiv: 2512.18272 by Andreas Sch\"omer, M\'aria Luk\'a\v{c}ov\'a-Medvi\v{d}ov\'a, Peter Virnau, Ranajay Datta.

Figure 1
Figure 1. Figure 1: (a) Shear viscosity η as function of shear rate γ˙ for dense (ρ = 0.8) binary blends of flexible (κ = 0) and stiffer (κ = 10) ring polymers, corresponding to different proportions (χ0) of flexible rings . Each ring consists of N = 15 monomers. Corresponding zero-shear viscosities, ηGK (calculated by the Green-Kubo relation) are shown on the y-axis. Note that the value of ηGK corresponding to κ = 10 as exhi… view at source ↗
Figure 2
Figure 2. Figure 2: (a) An equilibrated binary mixture of flexible (κ = 0, yellow) and stiffer (κ = 10, red) rings at χ0 = 0.5, confined within a channel bounded by particle-based walls (blue). (b) The same mixture under flow, induced by applying a constant force fx = 0.095 along the x-axis to all particles. (c) Density profiles of the respective components across the channel cross-section. (The inset depicts the velocity pro… view at source ↗
Figure 3
Figure 3. Figure 3: The potential functions f and g (left) and the mass/mean divergence error (right). 19 [PITH_FULL_IMAGE:figures/full_fig_p019_3.png] view at source ↗
Figure 4
Figure 4. Figure 4: ϕh(t, ·) at times t = 0.00, 10.00, 50.00, 500.00, 1000.00. 20 [PITH_FULL_IMAGE:figures/full_fig_p020_4.png] view at source ↗
Figure 5
Figure 5. Figure 5: ||uh(t, ·)||2 at times t = 10.00, 50.00, 500.00, 1000.00. The arrows indicate the flow direction and are scaled relative to max Ω {||uh(t, ·)||2} at the corresponding times. Results for χ = χcrit + 0.001 = 2 15 + 0.001. In this case, the Flory-Huggins interaction parameter is slightly above the critical value χcrit = 2/15, whence the potential function f has two minima that are close to 0.5 (cf. the green … view at source ↗
Figure 6
Figure 6. Figure 6: The potential functions f and g (left) and the mass/mean divergence error (right). 22 [PITH_FULL_IMAGE:figures/full_fig_p022_6.png] view at source ↗
Figure 7
Figure 7. Figure 7: ϕh(t, ·) at times t = 0.00, 10.00, 50.00, 500.00, 1000.00 Results for χ = 2 15 − 0.001. In this case, the Flory-Huggins interaction parameter is slightly below the critical value χcrit = 2/15, whence the potential function f has only one minimum at ϕ⋆ = ϕ ⋆ = 0.5 (cf. the green circle in [PITH_FULL_IMAGE:figures/full_fig_p023_7.png] view at source ↗
Figure 8
Figure 8. Figure 8: ). As a consequence, the components do not separate (cf [PITH_FULL_IMAGE:figures/full_fig_p023_8.png] view at source ↗
Figure 9
Figure 9. Figure 9: ϕh(t, ·) at times t = 0.00, 10.00, 50.00, 500.00, 1000.00 24 [PITH_FULL_IMAGE:figures/full_fig_p024_9.png] view at source ↗
read the original abstract

We model the flow behaviour of dense melts of flexible and semiflexible ring polymers in the presence of walls using a hybrid multiscale approach. Specifically, we perform molecular dynamics simulations and apply the Irving-Kirkwood formula to determine an averaged stress tensor for a macroscopic model. For the latter, we choose a Cahn-Hilliard-Navier-Stokes system with dynamic and no-slip boundary conditions. We present numerical simulations of the macroscopic flow that are based on a finite element method. In particular, we present detailed proofs of the solvability and the energy stability of our numerical scheme. Phase segregation under flow between flexible and semiflexible rings, as observed in the microscopic simulations, can be replicated in the macroscopic model by introducing effective attractive forces.

Editorial analysis

A structured set of objections, weighed in public.

Desk editor's note, referee report, simulated authors' rebuttal, and a circularity audit. Tearing a paper down is the easy half of reading it; the pith above is the substance, this is the friction.

Referee Report

2 major / 2 minor

Summary. The manuscript develops a hybrid multiscale method for the flow of dense melts of flexible and semiflexible ring polymers near walls. Molecular dynamics trajectories are processed with the Irving-Kirkwood formula to obtain an averaged stress tensor that is inserted into a Cahn-Hilliard-Navier-Stokes system equipped with dynamic and no-slip boundary conditions. Finite-element discretizations are analyzed with proofs of solvability and energy stability, and numerical experiments are presented. The central claim is that phase segregation observed in the microscopic simulations can be reproduced at the macroscopic level by the addition of effective attractive forces.

Significance. If the stress-tensor transfer is shown to be direct and the attractive forces are derived rather than introduced phenomenologically, the work would provide a concrete example of bottom-up multiscale coupling for complex fluids. The explicit energy-stability proofs for the numerical scheme constitute a clear technical contribution that strengthens the reliability of the simulations.

major comments (2)
  1. [Abstract] Abstract and the paragraph describing the hybrid construction: the claim that the macroscopic model replicates microscopic phase segregation rests on the introduction of effective attractive forces, yet the text gives no indication that these forces are computed from the same Irving-Kirkwood stress tensor extracted from the MD trajectories. If the forces are an independent modeling choice, the replication is not a direct consequence of the hybrid stress transfer.
  2. [Section on the macroscopic model] Section on the macroscopic model and the insertion step: it is not shown whether the CHNS system with only the IK-derived stress tensor (and the stated dynamic/no-slip boundary conditions) already produces the observed segregation or whether the attractive forces are required as an extra term. This distinction is load-bearing for the assertion that the hybrid method itself replicates the segregation.
minor comments (2)
  1. [Boundary conditions] The precise definition of the dynamic boundary condition and its coupling to the Cahn-Hilliard variable should be stated explicitly, preferably with an equation reference.
  2. Notation for the averaged stress tensor obtained from the Irving-Kirkwood formula could be made uniform between the MD post-processing and the CHNS momentum equation.

Simulated Author's Rebuttal

2 responses · 0 unresolved

We thank the referee for the careful reading and the constructive major comments. We agree that the distinction between the Irving-Kirkwood stress transfer and the additional effective forces requires explicit clarification to prevent any implication that the forces are derived from the stress tensor. We address each point below and will revise the manuscript accordingly.

read point-by-point responses
  1. Referee: [Abstract] Abstract and the paragraph describing the hybrid construction: the claim that the macroscopic model replicates microscopic phase segregation rests on the introduction of effective attractive forces, yet the text gives no indication that these forces are computed from the same Irving-Kirkwood stress tensor extracted from the MD trajectories. If the forces are an independent modeling choice, the replication is not a direct consequence of the hybrid stress transfer.

    Authors: We agree with the observation. The effective attractive forces are introduced as a separate modeling choice, informed by the microscopic observations but not computed from the Irving-Kirkwood stress tensor. The hybrid construction transfers the averaged stress tensor obtained via the Irving-Kirkwood formula into the Cahn-Hilliard-Navier-Stokes system; the forces constitute an additional term required to reproduce the phase segregation. We will revise the abstract and the paragraph on the hybrid construction to state this distinction explicitly. revision: yes

  2. Referee: [Section on the macroscopic model] Section on the macroscopic model and the insertion step: it is not shown whether the CHNS system with only the IK-derived stress tensor (and the stated dynamic/no-slip boundary conditions) already produces the observed segregation or whether the attractive forces are required as an extra term. This distinction is load-bearing for the assertion that the hybrid method itself replicates the segregation.

    Authors: The manuscript does not claim or demonstrate that the CHNS system with only the IK-derived stress tensor produces the segregation. The abstract states that replication occurs by introducing the effective attractive forces as an extra term. We will add a clarifying sentence in the section describing the macroscopic model and the insertion step to emphasize that the forces are required in addition to the stress tensor. revision: yes

Circularity Check

0 steps flagged

No circularity: stress extraction and force addition remain independent modeling steps

full rationale

The derivation proceeds from MD trajectories to IK-averaged stress tensor, direct insertion into the CHNS system, followed by separate introduction of effective attractive forces to match observed segregation. No equation or claim reduces a prediction to a fitted parameter by construction, nor does any load-bearing step rely on self-citation or an ansatz smuggled from prior author work. The solvability and stability proofs for the numerical scheme are self-contained mathematical results. The effective forces are presented as an additional modeling choice after observation, not as a quantity derived from the same IK data used to define the stress tensor.

Axiom & Free-Parameter Ledger

1 free parameters · 2 axioms · 0 invented entities

The central claim rests on the validity of stress averaging from MD trajectories and on the modeling decision to add effective attractive forces; both are domain assumptions rather than derived quantities.

free parameters (1)
  • effective attractive forces
    Introduced ad hoc in the macroscopic model to reproduce phase segregation observed in the microscopic simulations.
axioms (2)
  • domain assumption The Irving-Kirkwood formula yields an averaged stress tensor suitable for direct insertion into the macroscopic Cahn-Hilliard-Navier-Stokes system.
    Used to close the hybrid coupling (abstract description of the multiscale approach).
  • domain assumption The chosen dynamic and no-slip boundary conditions are compatible with the macroscopic model for polymer melts near walls.
    Stated as part of the macroscopic model setup.

pith-pipeline@v0.9.0 · 5679 in / 1425 out tokens · 30242 ms · 2026-05-25T07:51:45.456929+00:00 · methodology

discussion (0)

Sign in with ORCID, Apple, or X to comment. Anyone can read and Pith papers without signing in.

Reference graph

Works this paper leans on

58 extracted references · 58 canonical work pages

  1. [1]

    Abels, D

    H. Abels, D. Depner, and H. Garcke. Existence of Weak Solutions for a Diffuse Interface Model for Two-Phase Flows of Incompressible Fluids with Different Densities.J. Math. Fluid Mech., 15:453–480, 2013

  2. [2]

    Abels, D

    H. Abels, D. Depner, and H. Garcke. On an incompressible Navier–Stokes/Cahn–Hilliard system with degen- erate mobility.Ann. Inst. H. Poincaré Anal. Non Linéaire, 30(6):1175–1190, 2013

  3. [3]

    Abels, L

    H. Abels, L. Diening, and Y. Terasawa. Existence of weak solutions for a diffuse interface model of non- Newtonian two-phase flows.IMA J. Numer. Anal., 35:149–157, 2015

  4. [4]

    Abels, H

    H. Abels, H. Garcke, and A. Giorgini. Global regularity and asymptotic stabilization for the incompressible Navier–Stokes-Cahn–Hilliard model with unmatched densities.Math. Ann., 389:1267–1321, 2024

  5. [5]

    Abels, H

    H. Abels, H. Garcke, and G. Grün. Thermodynamically Consistent, Frame Indifferent Diffuse Interface Models for Incompressible Two-Phase Flows with Different Densities.Math. Models Methods Appl. Sci., 22(03):1150013, 2012

  6. [6]

    R. A. Adams and J. J. F. Fournier.Sobolev Spaces, volume 140 ofPure Appl. Math.Elsevier/Academic Press, Amsterdam, 2nd edition, 2003

  7. [7]

    M. P. Allen and D. J. Tildesley.Computer Simulation of Liquids. Clarendon Press, 1987

  8. [8]

    L. C. Berselli, L. Diening, and M. Růžička. Optimal error estimate for semi-implicit space-time discretization for the equations describing incompressible generalized Newtonian fluids.Nonlinear Anal. Real World Appl., 15(2):680–697, 2014

  9. [9]

    Binder, T

    K. Binder, T. Kreer, and A. Milchev. Polymer brushes under flow and in other out-of-equilibrium conditions. Soft Matter, 7:7159–7172, 2011

  10. [10]

    R. B. Bird, C. F. Curtiss, R. C. Armstrong, and O. Hassager.Dynamics of polymeric liquids,volumes 1 and 2. Wiley, 2nd edition, 1987

  11. [11]

    Blechta, J

    J. Blechta, J. Málek, and K. R. Rajagopal. On the Classification of Incompressible Fluids and a Mathematical Analysis of the Equations That Govern Their Motion.SIAM J. Math. Anal., 52(2):1232–1289, 2020

  12. [12]

    F. Boyer. Mathematical study of multi-phase flow under shear through order parameter formulation.Asymptot. Anal., 20(2):175–212, 1999

  13. [13]

    Brezzi and M

    F. Brezzi and M. Fortin.Mixed and Hybrid Finite Element Methods, volume 15 ofSpringer Ser. Comput. Math.Springer New York, 1991

  14. [14]

    Brunk, H

    A. Brunk, H. Egger, O. Habrich, and M. Lukáčová-Medviďová. A second-order fully-balanced structure- preserving variational discretization scheme for the Cahn–Hilliard–Navier–Stokes system.Math. Models Meth- ods Appl. Sci., 33(12):2587–2627, 2023. 26

  15. [15]

    Bulíček, F

    M. Bulíček, F. Ettwein, P. Kaplický, and D. Pražák. On uniqueness and time regularity of flows of power-law like non-Newtonian fluids.Math. Models Appl. Sci., 33:1995–2010, 2010

  16. [16]

    Bulíček, P

    M. Bulíček, P. Kaplický, and D. Pražák. Uniqueness and regularity of flows of non-Newtonian fluids with critical power-law growth.Math. Models Appl. Sci., 29(6):1207–1225, 2019

  17. [17]

    Bulíček, J

    M. Bulíček, J. Málek, and K. R. Rajagopal. Navier’s slip and evolutionary Navier-Stokes-like systems with pressure and shear-rate dependent viscosity.Indiana Univ. Math. J., 56:51–85, 2007

  18. [18]

    Cherfils and M

    L. Cherfils and M. Petcu. A numerical analysis of the Cahn–Hilliard equation with non-permeable walls. Numer. Math., 128(3):517–549, 2014

  19. [19]

    Datta, F

    R. Datta, F. Berressem, F. Schmid, A. Nikoubashman, and P. Virnau. Viscosity of Flexible and Semiflexible Ring Melts: Molecular Origins and Flow-Induced Segregation.Macromolecules, 56(18):7247–7255, 2023

  20. [20]

    Datta, L

    R. Datta, L. Yelash, F. Schmid, F. Kummer, M. Oberlack, M. Lukáčová-Medviďová, and P. Virnau. Shear- Thinning in Oligomer Melts—Molecular Origins and Applications.Polymers, 13(16):2806, 2021

  21. [21]

    Influence of topology on rheological properties of polymer ring melts.J

    Ranajay Datta and Peter Virnau. Influence of topology on rheological properties of polymer ring melts.J. Chem. Phys., 162(9), 2025

  22. [22]

    Diestel and J

    J. Diestel and J. J. Uhl, Jr.Vector Measures, volume 15 ofMath. Surveys Monogr.American Mathematical Society, Providence, RI, 1977

  23. [23]

    Dobrowolski.Angewandte Funktionalanalysis: Funktionalanalysis, Sobolev-Räume und elliptische Differen- tialgleichungen

    M. Dobrowolski.Angewandte Funktionalanalysis: Funktionalanalysis, Sobolev-Räume und elliptische Differen- tialgleichungen. Masterclass. Springer Berlin Heidelberg, 2., korrigierte und überarbeitete Auflage, 2010

  24. [24]

    Doi and S

    M. Doi and S. F. Edwards.The Theory of Polymer Dynamics. Clarendon Press, 1988

  25. [25]

    C. Duan, F. Zhou, K. Jiang, and T. Yu. Molecular dynamics simulation of planar Poiseuille flow for polymer melts in atomically flat nanoscale channel.Int. J. Heat Mass Transfer, 91:1088–1100, 2015

  26. [26]

    D. J. Evans. The frequency dependent shear viscosity of methane.Mol. Phys., 37(6):1745–1754, 1979

  27. [27]

    D. J. Evans and B. L. Holian. The Nose–Hoover thermostat.J. Chem. Phys., 83(8):4069–4074, 1985

  28. [28]

    D. J. Evans and G. Morriss.Statistical Mechanics of Nonequilibrium Liquids. Cambridge University Press, 2nd edition, 2008

  29. [29]

    D. J. Evans and G. P. Morriss. Nonlinear-response theory for steady planar Couette flow.Phys. Rev. A, 30:1528–1530, 1984

  30. [30]

    H. P. Fischer, P. Maass, and W. Dieterich. Novel Surface Modes in Spinodal Decomposition.Phys. Rev. Lett., 79:893–896, 1997

  31. [31]

    C. G. Gal, M. Grasselli, and H. Wu. Global Weak Solutions to a Diffuse Interface Model for Incompressible Two-Phase Flows with Moving Contact Lines and Different Densities.Arch. Ration. Mech. Anal., 234:1–56, 2019

  32. [32]

    Giorgini

    A. Giorgini. Existence and stability of strong solutions to the Abels–Garcke–Grün model in three dimensions. Interfaces Free Bound., 24(4):565–608, 2022

  33. [33]

    G. Grün, F. Guillén-González, and S. Metzger. On Fully Decoupled, Convergent Schemes for Diffuse Interface Models for Two-Phase Flow with General Mass Densities.Commun. Comput. Phys., 19(5):1473–1502, 2016

  34. [34]

    Guillén-González and G

    F. Guillén-González and G. Tierra. Splitting Schemes for a Navier-Stokes-Cahn-Hilliard Model for Two Fluids with Different Densities.J. Comput. Math., 32(6):643–664, 2014

  35. [35]

    Guillén-González and G

    F. Guillén-González and G. Tierra. Structure preserving finite element schemes for the Navier-Stokes-Cahn- Hilliard system with degenerate mobility.Comput. Math. Appl., 172:181–201, 2024

  36. [36]

    D. P. Hansen and D. J. Evans. A Parallel Algorithm for Nonequilibrium Molecular Dynamics Simulation of Shear Flow on Distributed Memory Machines.Mol. Simul., 13(6):375–393, 1994. 27

  37. [37]

    J. H. Irving and J. G. Kirkwood. The Statistical Mechanical Theory of Transport Processes. IV. The Equations of Hydrodynamics.J. Chem. Phys., 18(6):817–829, 1950

  38. [38]

    Knopf and J

    P. Knopf and J. Stange. A thermodynamically consistent model for bulk-surface viscous fluid mixtures: Model derivation and mathematical analysis,arXiv:2509.11925 [math.AP], 2025

  39. [39]

    Kratky and G

    O. Kratky and G. Porod. Röntgenuntersuchung gelöster Fadenmoleküle.Rec. Trav. Chim. Pays-Bas, 68(12):1106–1122, 1949

  40. [40]

    Kremer and G

    K. Kremer and G. S. Grest. Dynamics of entangled linear polymer melts: A molecular-dynamics simulation. J. Chem. Phys., 92(8):5057–5086, 1990

  41. [41]

    A. J. C. Ladd. Equations of motion for non-equilibrium molecular dynamics simulations of viscous flow in molecular fluids.Mol. Phys., 53(2):459–463, 1984

  42. [42]

    Logg, K.A

    A. Logg, K.A. Mardal, and G. N. Wells.Automated solution of differential equations by the finite element method. The FEniCS book, volume 84 ofLect. Notes Comput. Sci. Eng.Springer, Heidelberg, 2012

  43. [43]

    Mitrea and M

    I. Mitrea and M. Mitrea.Multi-Layer Potentials and Boundary Problems for Higher-Order Elliptic Systems in Lipschitz Domains, volume 2063 ofLecture Notes in Math.Springer, Heidelberg, 2013

  44. [44]

    Nečas.Direct Methods in the Theory of Elliptic Equations

    J. Nečas.Direct Methods in the Theory of Elliptic Equations. Springer Monogr. Math. Springer, Heidelberg, Corrected 2nd printing 2012. Translated from the 1967 French original by G. Tronel and A. Kufner, editorial coordination and preface by Š. Nečasová and a contribution by C. G. Simader

  45. [45]

    Pastorino and A

    C. Pastorino and A. Gama Goicochea. Dissipative Particle Dynamics: A Method to Simulate Soft Matter Sys- tems in Equilibrium and Under Flow. InSelected Topics of Computational and Experimental Fluid Mechanics, pages 51–79, Cham, 2015. Springer International Publishing

  46. [46]

    Pastorino, T

    C. Pastorino, T. Kreer, M. Müller, and K. Binder. Comparison of dissipative particle dynamics and Langevin thermostats for out-of-equilibrium simulations of polymeric systems.Phys. Rev. E, 76:026706, Aug 2007

  47. [47]

    Pastorino and M

    C. Pastorino and M. Müller. Mixed brush of chemically and physically adsorbed polymers under shear: Inverse transport of the physisorbed species.J. Chem. Phys., 140(1):014901, 2014

  48. [48]

    Plimpton

    S. Plimpton. Fast Parallel Algorithms for Short-Range Molecular Dynamics.J. Comput. Phys., 117(1):1–19, 1995

  49. [49]

    Rubinstein and R

    M. Rubinstein and R. H. Colby.Polymer Physics. OUP Oxford, 2003

  50. [50]

    Ruiz Goldstein, A

    G. Ruiz Goldstein, A. Miranville, and G. Schimperna. A Cahn-Hilliard model in a domain with non-permeable walls.Phys. D, 240(8):754–766, 2011

  51. [51]

    Schaefer

    H. Schaefer. Über die Methode der a priori-Schranken.Math. Ann., 129:415–416, 1955

  52. [52]

    Soddemann, B

    T. Soddemann, B. Dünweg, and K. Kremer. Dissipative particle dynamics: A useful thermostat for equilibrium and nonequilibrium molecular dynamics simulations.Phys. Rev. E, 68:046702, Oct 2003

  53. [53]

    Srivastva and A

    D. Srivastva and A. Nikoubashman. Flow Behavior of Chain and Star Polymers and Their Mixtures.Polymers, 10(6):599, 2018

  54. [54]

    Temam.Infinite-Dimensional Dynamical Systems in Mechanics and Physics, volume 68 ofAppl

    R. Temam.Infinite-Dimensional Dynamical Systems in Mechanics and Physics, volume 68 ofAppl. Math. Sci. Springer-Verlag, New York, 2nd edition, 1997

  55. [55]

    B. D. Todd and P. J. Daivis.Nonequilibrium Molecular Dynamics: Theory, Algorithms and Applications. Cambridge University Press, 2017

  56. [56]

    M. E. Tuckerman, C. J. Mundy, S. Balasubramanian, and M. L. Klein. Modified nonequilibrium molecular dynamics for fluid flows with energy conservation.J. Chem. Phys., 106(13):5615–5621, 1997

  57. [57]

    J. D. Weeks, D. Chandler, and H. C. Andersen. Role of repulsive forces in determining equilibrium structure of simple liquids.J. Chem. Phys., 54(12):5237–5247, 1971

  58. [58]

    Weiss, Christos N

    Lisa B. Weiss, Christos N. Likos, and Arash Nikoubashman. Spatial Demixing of Ring and Chain Polymers in Pressure-Driven Flow.Macromolecules, 52(20):7858–7869, 2019. 28 A Viscosity fitting In the following, we list the values for the parameters{ηi,0, ηi,∞, ai,1, ai,2, ai,3}i= 0,...,6 resulting from a least-squares fitting of the MD data shown in Figure 1a...