Viscosity calculations of <b>
                     <i>n</i>
                  </b>-alkanes by equilibrium molecular dynamics

Mondello, Maurizio; Grest, Gary S.

doi:10.1063/1.474002

Cited by 220 publications

(249 citation statements)

References 33 publications

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“…Using this method, Mondello et al showed that 0 of medium long chains may be estimated from the longest relaxation time measured in EMD simulations by invoking the Rouse model. 5,6 They found that the estimates are in good agreement with extrapolated NEMD results ͑within 20%͒. Moore et al have performed NEMD simulations of a C 100 melt ͑close to our C 120 ͒ at various shear rates.…”

Section: Introductionsupporting

confidence: 53%

“…24 Several simulation studies have shown this to be correct. 5,11 The difference between the viscosity calculated from the molecular tensor and that from the atomic tensor is found to converge to zero much faster than the longest relaxation time of the molecule. This was confirmed in test runs of our system in which we calculated the shear relaxation modulus from both atomic and molecular stress tensors.…”

Section: ͑11͒mentioning

confidence: 99%

“…Several other studies have been reported on simulations of melts of polymers of comparable size. [1][2][3][4][5][6][7][8][9] They all suggest that individual properties of these melts can well be described by the Rouse model. 10 In this paper we will test whether the Rouse model can be used to predict the time correlation functions of a comprehensive set of physical processes by using one single set of parameters.…”

Section: Introductionmentioning

confidence: 99%

“…3 Mondello and coworkers investigated a number of chain lengths between C 10 and C 66 . 5,6 By use of the Green-Kubo ͑GK͒ relation they were able to calculate the zero-shear viscosity 0 for chains up to C 16 by integrating the zero-shear stress relaxation curves obtained from equilibrium molecular dynamics simulations ͑EMD͒. They were not able to determine the viscosity by this method for chains longer than C 16 .…”

Section: Introductionmentioning

confidence: 99%

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Zero-shear stress relaxation and long time dynamics of a linear polyethylene melt: A test of Rouse theory

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Briels

2001

The Journal of Chemical Physics

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Effects of alignment layer thickness on the pretilt angle of liquid crystals APL: Org. Electron. Photonics 3, 270 (2010) Effects of alignment layer thickness on the pretilt angle of liquid crystals Appl. Phys. Lett. 97, 243306 (2010) Field-theoretic model of inhomogeneous supramolecular polymer networks and gels J. Chem. Phys. 133, 174903 (2010) Origin of translocation barriers for polyelectrolyte chains JCP: BioChem. Phys Results of united atom molecular dynamics simulations of a n-C 120 H 242 melt at 450 K are presented. It is shown that the results of mean square displacement, dynamic structure factor, end-to-end vector autocorrelation, and shear relaxation modulus can consistently be described by the Rouse model with a single set of fit parameters, provided the length scales involved are larger than the statistical segment length bϷ1.2 nm. On smaller length scales the stiffness of the chain becomes prominent, and the results deviate increasingly from the Rouse predictions. The shear relaxation modulus G(t) is determined from the stress autocorrelation function from both atomic and molecular points of view. The integrals ͐G(t)dt are found to be identical after 1 ps and a Rouse description is shown to coincide for time scales larger than 0.4 ns. Compared to experimental values, the measured diffusion coefficient is overestimated by 63% and the viscosity is underestimated by 38%, consistent with molecular dynamics simulations of small molecules.

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Section: Introductionsupporting

confidence: 53%

Section: ͑11͒mentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 2 more Smart Citations

Zero-shear stress relaxation and long time dynamics of a linear polyethylene melt: A test of Rouse theory

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Briels

2001

The Journal of Chemical Physics

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“…One should notice that at the particular state point of 423.15 K and 1 MPa, which corresponds to the lowest density considered, all models examined showed the least accurate behavior. Earlier studies for pure n-alkanes by Mondello et al [62][63][64] have shown overestimation of self-diffusion coefficients by UA force fields.…”

Section: Diffusion Coefficient and Viscosity Calculations The Diffusmentioning

confidence: 99%

Atomistic Molecular Dynamics Simulations of Carbon Dioxide Diffusivity in n-Hexane, n-Decane, n-Hexadecane, Cyclohexane, and Squalane

et al. 2016

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Atomistic molecular dynamics simulations were carried out to obtain the diffusion coefficients of CO2 in n-hexane, n-decane, n-hexadecane, cyclohexane and squalane at temperatures up to 423.15 K and pressures up to 65 MPa. Three popular models were used for the representation of hydrocarbons: the united atom TraPPE (TraPPE-UA), the all-atom OPLS, and an optimized version of OPLS, namely L-OPLS. All models qualitatively reproduce the pressure dependence of diffusion coefficient of CO2 in hydrocarbons measured recently, and L-OPLS was found to be the most accurate. Specifically for n-alkanes, L-OPLS also reproduced the measured viscosities and densities much more accurately than the original OPLS and TraPPE-UA models, indicating that the optimization of the torsional potential is crucial for the accurate description of transport properties of long chain molecules. The three force fields predict different microscopic properties such as mean square radius of gyration for the n-alkane molecules and pair correlation functions for the CO2 -n-alkane interactions. CO2 diffusion coefficients in all hydrocarbons studied are shown to deviate significantly from the Stokes-Einstein behavior.

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Atomistic Insights on the Rheological Property of Polycaprolactone Composites with the Addition of Graphene

Nie

Zhan

Kou

et al. 2021

Adv Materials Technologies

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Although polymer composites reinforced by graphene have been researched for almost two decades, the processing challenges caused by viscosity remains, especially for 3D printing. [3] Many experimental works have been conducted to assess the rheological properties of graphene reinforced composites, covering various factors such as weight/volume fraction, dispersion, surface modification, and shear rate. [4] However, the influence of the graphene size has not been systematically studied experimentally due to the intrinsic complexities and challenges for sample preparation with controlled micro/nanoscale features. In particular, the influence of 2D nanoscale fillers on the rheological properties of polymer composites remains unclear. With such experimental difficulties, numerical modeling or simulation becomes a powerful tool to probe the rheological properties of polymer composites at the micro and nano scales. Different modeling approaches have been developed for such purposes, such as the multiscale method, coarse grain (CG) method, and molecular dynamic (MD) simulation. For instance, the multiscale method has been well-developed to predict the mechanical performance of carbon-reinforced composites. [5] Compared with the multiscale and CG methods, MD simulation can exploit the influences from nanoscale reinforcements on the rheological properties of polymer composites at an atomistic level. Many works have investigated the effect of the size of nanoparticle reinforcements on the composite's viscosity based on MD simulations. Grant et al. [6] identified that viscosity could be influenced by the nanoparticle volume fraction, interface area, and the interaction between particle and polymer. Francis et al. [7] found that the composite viscosity would decrease when small particles aggregate into a large cluster. More recent work found that the composite viscosity depends on the relation between particle size and polymer entanglement length. Jagannathan et al. [8] discovered that if the particle size is smaller than the polymer entanglement length, the composite viscosity will reduce and vice versa. Ting et al. [9] chose a group of particles smaller than the polymer entanglement length and found that the viscosity increases with increasing particle size while the interaction between the polymer and particle changes from slippery to sticky. Overall, when the particle size is around the polymer entanglement length, the viscosity increases with To facilitate the biomedical applications of biocomposites, researchers have used different types of fillers to enhance their mechanical properties. However, the addition of fillers not only changes the mechanical performance of the biocomposites, but also affects their printability, that is, their rheological properties. With the aid of atomistic simulations, this work investigates the influence of graphene size and aggregation on the rheological properties of polycaprolactone (PCL) composites. For the same weight ratio, increasing the graphene size causes the viscosity of the ...

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Viscosity calculations of n -alkanes by equilibrium molecular dynamics

Cited by 220 publications

References 33 publications

Zero-shear stress relaxation and long time dynamics of a linear polyethylene melt: A test of Rouse theory

Zero-shear stress relaxation and long time dynamics of a linear polyethylene melt: A test of Rouse theory

Atomistic Molecular Dynamics Simulations of Carbon Dioxide Diffusivity in n-Hexane, n-Decane, n-Hexadecane, Cyclohexane, and Squalane

Atomistic Insights on the Rheological Property of Polycaprolactone Composites with the Addition of Graphene

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