Shear viscosity calculations through a reverse nonequilibrium method

Cavalcanti, Welchy Leite; Chen, X.; Müller‐Plathe, Florian

doi:10.1002/pssa.200675201

Cited by 7 publications

(10 citation statements)

References 15 publications

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“…It is called “reverse” because the cause and effect are reversed with respect to experiment and the conventional nonequilibrium simulation methods. The method has been successfully extended to simulate molecular fluids, , complex fluids, , polymers, , and ionic liquids . Here we briefly describe the basic elements of the method, with the main emphasis on confined fluids.…”

Section: Methodsmentioning

confidence: 99%

Viscosity of Nanoconfined Polyamide-6,6 Oligomers: Atomistic Reverse Nonequilibrium Molecular Dynamics Simulation

Eslami

Müller‐Plathe

2009

J. Phys. Chem. B

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Our new simulation scheme in isosurface-isothermal-isobaric ensemble [Eslami, H.; Mozaffari, F.; Moghadasi, J.; Müller-Plathe, F. J. Chem. Phys. 2008, 129, 194702], developed to simulate confined fluids in equilibrium with bulk, is applied to simulate polyamide-6,6 oligomers confined between graphite surfaces. The reverse nonequilibrium molecular dynamics simulation technique is employed to shear the graphite surfaces. In this work, six confined systems, with different surface separations, as well as the bulk fluid are simulated. Our results show a viscosity increase with respect to the bulk fluid, with decreasing distance between surfaces. Also, the calculated viscosities of the confined systems show an oscillatory behavior with maxima corresponding to well-formed layers between the surfaces. We observe a substantial slip at the surfaces, with the slip length depending on the shear rate and on the slit width. The slip length and the slip velocity show oscillatory behavior with out-of-phase oscillations with respect to the solvation force oscillations. Moreover, the temperature difference between coldest and hottest parts of the simulation box depends on the shear rate and on the layering effect (solvation force oscillations). An analysis of oligomer deformation under flow shows preferential alignment of oligomers parallel to the surfaces with increasing shear rate.

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Section: Methodsmentioning

confidence: 99%

Viscosity of Nanoconfined Polyamide-6,6 Oligomers: Atomistic Reverse Nonequilibrium Molecular Dynamics Simulation

Eslami

Müller‐Plathe

2009

J. Phys. Chem. B

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“…The RNEMD simulations impose an artificial momentum flux between two regions of the simulation, and the velocity gradient is the fluid's response. This technique has now been applied quite widely to determine the viscosities of a number of bulk fluids [46][47][48].…”

Section: B Solid-liquid Friction Of the Interfacesmentioning

confidence: 99%

The different facets of ice have different hydrophilicities: Friction at water / ice-I$_\mathrm{h}$ interfaces

Louden¹,

Gezelter²

2015

Preprint

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We present evidence that the prismatic and secondary prism facets of ice-I h crystals possess structural features that can reduce the effective hydrophilicity of the ice/water interface. The spreading dynamics of liquid water droplets on ice facets exhibits long-time behavior that differs for the prismatic {10 10} and secondary prism {11 20} facets when compared with the basal {0001} and pyramidal {20 21} facets. We also present the results of simulations of solid-liquid friction of the same four crystal facets being drawn through liquid water, and find that the two prismatic facets exhibit roughly half the solid-liquid friction of the basal and pyramidal facets. These simulations provide evidence that the two prismatic faces have a significantly smaller effective surface area in contact with the liquid water. The ice / water interfacial widths for all four crystal facets are similar (using both structural and dynamic measures), and were found to be independent of the shear rate. Additionally, decomposition of orientational time correlation functions show position-dependence for the short-and longer-time decay components close to the interface.

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“…A number of molecular methods have been applied over the last years for estimating macroscopic transport properties of fluids. [110][111][112] The applied techniques can be broadly classified as belonging either to the equilibrium (EMD) or nonequilibrium (NEMD) molecular dynamics. The equilibrium techniques utilize the fluctuation-dissipation theorem and determine macroscopic properties through appropriate Einstein or Green-Kubo relations.…”

Section: Transport Coefficientsmentioning

confidence: 99%

“…The RNEMD method offers superior characteristics in terms of performance, accuracy, and applicability. 110 …”

Section: Transport Coefficientsmentioning

confidence: 99%

“…In the opposite direction, above the middle of the channel, there is a physical transfer of momentum arising as a response of the system to the imposed nonequilibrium state. 110,112 In a steady state, the transfer of momentum due to the physical and artificial mechanisms is the same. This can be expressed as follows:…”

Section: Reverse Nonequilibrium Molecular Dynamicsmentioning

confidence: 99%

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