Screening properties of four mesoscale smoothed charge models, with application to dissipative particle dynamics

Warren, Patrick B.; Vlasov, A. Yu.

doi:10.1063/1.4866375

Cited by 47 publications

(76 citation statements)

References 25 publications

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“…Lastly, we perform an additional test of the use of point charges in DPD by predicting the scaling exponent of the gyration radius, Rg, as a function of the polymerization degree for 20 polyelectrolytes in solution under increasing ionic strength. It is well known [32] that for neutral polymers the radius of gyration scales with the polymerization degree N (not to be confused here with the coarsegraining degree, Nm) as ~, where is the scaling exponent, and it is known to depend on the quality of the solvent, and the dimensionality of the system.…”

Section: Resultsmentioning

confidence: 99%

Electrostatics in dissipative particle dynamics using Ewald sums with point charges

Terrón-Mejía

López-Rendón

Goicochea

2016

J. Phys.: Condens. Matter

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A proper treatment of electrostatic interactions is crucial for the accurate calculation of forces in computer simulations. Electrostatic interactions are typically modeled using Ewaldbased methods, which have become one of the cornerstones upon which many other methods for the numerical computation of electrostatic interactions are based. However, their use with charge distributions rather than point charges requires the inclusion of ansatz for the solutions of the Poisson equation, since there is no exact solution known for smeared out charges. The interest for incorporating electrostatic interactions at the scales of length and time that are relevant for the study the physics of soft condensed matter has increased considerably. Using mesoscale simulation techniques, such as dissipative particle dynamics (DPD), allows us to reach longer time scales in numerical simulations, without abandoning the particulate description of the problem. The main problem with incorporating electrostatics into DPD simulations is that DPD particles are soft and those particles with opposite charge can form artificial clusters of ions. Here we show that one can incorporate the electrostatic interactions through Ewald sums with point charges in DPD if larger values of coarse -graining degree are used, where DPD is truly mesoscopic. Using point charges with larger excluded volume interactions the artificial formation of ionic pairs with point charges can be avoided, and one obtains correct predictions. We establish ranges of parameters useful for detecting boundaries where artificial formation of ionic pairs occurs. Lastly, using point charges we predict the scaling properties of polyelectrolytes in solvents of varying quality and obtain predictions that are in agreement with calculations that use other methods, and with recent experimental results.

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Section: Resultsmentioning

confidence: 99%

Electrostatics in dissipative particle dynamics using Ewald sums with point charges

Terrón-Mejía

López-Rendón

Goicochea

2016

J. Phys.: Condens. Matter

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“…A more detailed analysis is needed to explore the effect of different choices, not just for the Ewald part, but also for the parameter 1/λ controlling the decay of the charge distribution or the charge distribution itself. In this sense, the recent study performed by Warren and Vlasov is valuable 55 . The Slater distribution assigned on charged particles was used with the value of β * = β R c = R c /λ = 0.929 34 .…”

Section: Systems and Simulation Detailsmentioning

confidence: 96%

The structure and interaction mechanism of a polyelectrolyte complex: a dissipative particle dynamics study

et al. 2015

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The mechanism of complex formation of two oppositely charged linear polyelectrolytes dispersed in a solvent is investigated by using dissipative particle dynamics (DPD) simulation. In the polyelectrolyte solution, the size of the cationic polyelectrolyte remains constant while the size of the anionic chain increases. We analyze the influence of the anionic polyelectrolyte size and salt effect (ionic strength) on the conformational changes of the chains during complex formation. The behavior of the radial distribution function, the end-to-end distance and the radius of gyration of each polyelectrolyte is examined. These results showed that the effectiveness of complex formation is strongly influenced by the process of counterion release from the polyelectrolyte chains. The radius of gyration of the complex is estimated using the Fox-Flory equation for a wormlike polymer in a theta solvent. The addition of salts in the medium accelerates the complex formation process, affecting its radius of gyration. Depending on the ratio of chain lengths a compact complex or a loosely bound elongated structure can be formed.

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“…The adopted dissection of the polymer into coarse-grained beads is performed to minimize the difference in volumes between the polymer fragments represented by from the bead center towards the periphery. 70 The choice of R e is rather arbitrary, since charge cloud size does not have a clear physical meaning, 71 its influence on the thermodynamic properties of electrolytes is still to be examined. We chose R e smaller than recommended by Groot in an attempt to improve calculation efficiency.…”

Section: Coarse-grained Model Of Metal-substituted Nafionmentioning

confidence: 99%

“…We chose R e smaller than recommended by Groot in an attempt to improve calculation efficiency. 71 The comparison between the screened and Coulomb potential created by two point charges is given in Supporting Information. The 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 11…”

Section: Coarse-grained Model Of Metal-substituted Nafionmentioning

confidence: 99%

Self-Assembly in Nafion Membranes upon Hydration: Water Mobility and Adsorption Isotherms

Vishnyakov

Neimark

2014

J. Phys. Chem. B

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By means of dissipative particle dynamics (DPD) and Monte Carlo (MC) simulations, we explored geometrical, transport, and sorption properties of hydrated Nafion-type polyelectrolyte membranes. Composed of a perfluorinated backbone with sulfonate side chains, Nafion self-assembles upon hydration and segregates into interpenetrating hydrophilic and hydrophobic subphases. This segregated morphology determines the transport properties of Nafion membranes that are widely used as compartment separators in fuel cells and other electrochemical devices, as well as permselective diffusion barriers in protective fabrics. We introduced a coarse-grained model of Nafion, which accounts explicitly for polymer rigidity and electrostatic interactions between anionic side chains and hydrated metal cations. In a series of DPD simulations with increasing content of water, a classical percolation transition from a system of isolated water clusters to a 3D network of hydrophilic channels was observed. The hydrophilic subphase connectivity and water diffusion were studied by constructing digitized replicas of self-assembled morphologies and performing random walk simulations. A non-monotonic dependence of the tracer diffusivity on the water content was found. This unexpected behavior was explained by the formation of large and mostly isolated water domains detected at high water content and high equivalent polymer weight. Using MC simulations, we calculated the chemical potential of water in the hydrated polymer and constructed the water sorption isotherms, which extended to the oversaturated conditions. We determined that the maximum diffusivity and the onset of formation of large water domains corresponded to the saturation conditions at 100% humidity. The oversaturated membrane morphologies generated in the canonical ensemble DPD simulations correspond to the metastable and unstable states of Nafion membrane that are not realized in the experiments.

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Screening properties of four mesoscale smoothed charge models, with application to dissipative particle dynamics

Cited by 47 publications

References 25 publications

Electrostatics in dissipative particle dynamics using Ewald sums with point charges

Electrostatics in dissipative particle dynamics using Ewald sums with point charges

The structure and interaction mechanism of a polyelectrolyte complex: a dissipative particle dynamics study

Self-Assembly in Nafion Membranes upon Hydration: Water Mobility and Adsorption Isotherms

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