Isomorph invariance of Couette shear flows simulated by the SLLOD equations of motion

Leila Separdar, Nicholas Bailey, Thomas Schrøder, Saeid Davatolhagh, J. C. Dyre

Publikation: Bidrag til tidsskriftTidsskriftartikelForskningpeer review

Resumé

Non-equilibrium molecular dynamics simulations were performed to study the thermodynamic, structural, and dynamical properties of the single-component Lennard-Jones and the Kob-Andersen binary Lennard-Jones liquids. Both systems are known to have strong correlations between equilibrium thermal fluctuations of virial and potential energy. Such systems have good isomorphs (curves in the thermodynamic phase diagram along which structural, dynamical, and some thermodynamic quantities are invariant when expressed in reduced units). The SLLOD equations of motion were used to simulate Couette shear flows of the two systems. We show analytically that these equations are isomorph invariant provided the reduced strain rate is fixed along the isomorph. Since isomorph invariance is generally only approximate, a range of strain rates were simulated to test for the predicted invariance, covering both the linear and nonlinear regimes. For both systems, when represented in reduced units the radial distribution function and the intermediate scattering function are identical for state points that are isomorphic. The strain-rate dependent viscosity, which exhibits shear thinning, is also invariant along an isomorph. Our results extend the isomorph concept to the non-equilibrium situation of a shear flow, for which the phase diagram is three dimensional because the strain rate defines a third dimension.
OriginalsprogEngelsk
Artikelnummer154505
TidsskriftJournal of Chemical Physics
Vol/bind138
Udgave nummer15
Antal sider11
ISSN0021-9606
DOI
StatusUdgivet - 2013

Citer dette

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title = "Isomorph invariance of Couette shear flows simulated by the SLLOD equations of motion",
abstract = "Non-equilibrium molecular dynamics simulations were performed to study the thermodynamic, structural, and dynamical properties of the single-component Lennard-Jones and the Kob-Andersen binary Lennard-Jones liquids. Both systems are known to have strong correlations between equilibrium thermal fluctuations of virial and potential energy. Such systems have good isomorphs (curves in the thermodynamic phase diagram along which structural, dynamical, and some thermodynamic quantities are invariant when expressed in reduced units). The SLLOD equations of motion were used to simulate Couette shear flows of the two systems. We show analytically that these equations are isomorph invariant provided the reduced strain rate is fixed along the isomorph. Since isomorph invariance is generally only approximate, a range of strain rates were simulated to test for the predicted invariance, covering both the linear and nonlinear regimes. For both systems, when represented in reduced units the radial distribution function and the intermediate scattering function are identical for state points that are isomorphic. The strain-rate dependent viscosity, which exhibits shear thinning, is also invariant along an isomorph. Our results extend the isomorph concept to the non-equilibrium situation of a shear flow, for which the phase diagram is three dimensional because the strain rate defines a third dimension.",
author = "Leila Separdar and Nicholas Bailey and Thomas Schr{\o}der and Saeid Davatolhagh and Dyre, {J. C.}",
year = "2013",
doi = "10.1063/1.4799273",
language = "English",
volume = "138",
journal = "Journal of Chemical Physics",
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Isomorph invariance of Couette shear flows simulated by the SLLOD equations of motion. / Separdar, Leila; Bailey, Nicholas; Schrøder, Thomas; Davatolhagh, Saeid; Dyre, J. C.

I: Journal of Chemical Physics, Bind 138, Nr. 15, 154505, 2013.

Publikation: Bidrag til tidsskriftTidsskriftartikelForskningpeer review

TY - JOUR

T1 - Isomorph invariance of Couette shear flows simulated by the SLLOD equations of motion

AU - Separdar, Leila

AU - Bailey, Nicholas

AU - Schrøder, Thomas

AU - Davatolhagh, Saeid

AU - Dyre, J. C.

PY - 2013

Y1 - 2013

N2 - Non-equilibrium molecular dynamics simulations were performed to study the thermodynamic, structural, and dynamical properties of the single-component Lennard-Jones and the Kob-Andersen binary Lennard-Jones liquids. Both systems are known to have strong correlations between equilibrium thermal fluctuations of virial and potential energy. Such systems have good isomorphs (curves in the thermodynamic phase diagram along which structural, dynamical, and some thermodynamic quantities are invariant when expressed in reduced units). The SLLOD equations of motion were used to simulate Couette shear flows of the two systems. We show analytically that these equations are isomorph invariant provided the reduced strain rate is fixed along the isomorph. Since isomorph invariance is generally only approximate, a range of strain rates were simulated to test for the predicted invariance, covering both the linear and nonlinear regimes. For both systems, when represented in reduced units the radial distribution function and the intermediate scattering function are identical for state points that are isomorphic. The strain-rate dependent viscosity, which exhibits shear thinning, is also invariant along an isomorph. Our results extend the isomorph concept to the non-equilibrium situation of a shear flow, for which the phase diagram is three dimensional because the strain rate defines a third dimension.

AB - Non-equilibrium molecular dynamics simulations were performed to study the thermodynamic, structural, and dynamical properties of the single-component Lennard-Jones and the Kob-Andersen binary Lennard-Jones liquids. Both systems are known to have strong correlations between equilibrium thermal fluctuations of virial and potential energy. Such systems have good isomorphs (curves in the thermodynamic phase diagram along which structural, dynamical, and some thermodynamic quantities are invariant when expressed in reduced units). The SLLOD equations of motion were used to simulate Couette shear flows of the two systems. We show analytically that these equations are isomorph invariant provided the reduced strain rate is fixed along the isomorph. Since isomorph invariance is generally only approximate, a range of strain rates were simulated to test for the predicted invariance, covering both the linear and nonlinear regimes. For both systems, when represented in reduced units the radial distribution function and the intermediate scattering function are identical for state points that are isomorphic. The strain-rate dependent viscosity, which exhibits shear thinning, is also invariant along an isomorph. Our results extend the isomorph concept to the non-equilibrium situation of a shear flow, for which the phase diagram is three dimensional because the strain rate defines a third dimension.

U2 - 10.1063/1.4799273

DO - 10.1063/1.4799273

M3 - Journal article

VL - 138

JO - Journal of Chemical Physics

JF - Journal of Chemical Physics

SN - 0021-9606

IS - 15

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ER -