Concentration and mass dependence of transport coefficients and correlation functions in binary mixtures with high mass asymmetry

We study two types of intrinsic uncertainties, statistical errors and system size effects, in estimating shear viscosity via equilibrium molecular dynamics simulations, and compare them with the corresponding uncertainties in evaluating the self-diffusion coefficient. Uncertainty quantification formulas for the statistical errors in the shear-stress autocorrelation function and shear viscosity are obtained under the assumption that shear stress follows a Gaussian process. Analyses of simulation results for simple and complex fluids reveal that the Gaussianity is more pronounced in the shear-stress process (related to shear viscosity estimation) compared with the velocity process of an individual molecule (related to self-diffusion coefficient). At relatively high densities corresponding to a liquid state, we observe that the shear viscosity exhibits complex size-dependent behavior unless the system is larger than a certain length scale, and beyond which, reliable shear viscosity values are obtained without any noticeable scaling behavior with respect to the system size. We verify that this size-dependent behavior is configurational and relate the characteristic length scale to the shear-stress correlation length.

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“…We report the normalized standard error, σ, defined in Eq. (10). Theoretically predicted error levels are computed from Eqs.…”

Section: A Estimation Of Statistical Uncertaintiesmentioning

confidence: 99%

Nature of intrinsic uncertainties in equilibrium molecular dynamics estimation of shear viscosity for simple and complex fluids

Kim

Han

Kim

et al. 2018

The Journal of Chemical Physics

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“…Such a possibility has sometimes been challenged [1,16]. Indeed, as already mentioned, the pinning protocol exactly preserves the configurational properties of the bulk fluid from which a PP system is prepared [1,2], but it can have a strong effect on the dynamics [1,[10][11][12][13][14][15][16][17][18][19][20][21]. At first sight, this looks incompatible with the use of the MCT, which is known to take only structural quantities as input in order to predict the dynamics.…”

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confidence: 99%

Mode-coupling theory predictions for the dynamical transitions of partly pinned fluid systems

Krakoviack

2011

Phys. Rev. E

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The predictions of the mode-coupling theory (MCT) for the dynamical arrest scenarios in a partly pinned (PP) fluid system are reported. The corresponding dynamical phase diagram is found to be very similar to that of a related quenched-annealed (QA) system. The only significant qualitative difference lies in the shape of the diffusion-localization lines at high matrix densities, with a reentry phenomenon for the PP system but not for the QA model, in full agreement with recent computer simulation results. This finding clearly lends support to the predictive power of the MCT for fluid-matrix systems. In addition, the predictions of the MCT are shown to be in stark contrast with those of the random first-order transition theory. The PP systems are thus confirmed as very promising models for differentiating tests of theories of the glass transition.

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“…Accordingly, they have regularly appeared in computational studies of the dynamics of fluids in confinement, 2,[6][7][8][9][10][11][12][13][14][15][16][17][18][19][20][21][22][23] where their peculiar properties open up some interesting perspectives. Indeed, since the pinning process leaves the average configurational properties of a PP fluid system identical to those of the bulk fluid from which it is prepared, meaning in particular a perfectly flat average density profile and unperturbed pair correlations, one might argue that the study of PP systems gives access to the intrinsic dynamical effects of confinement, based on the fact that the possibility of interfering secondary effects originating in confinement-induced structural changes has been virtually eliminated by construction.…”

Section: Introductionmentioning

confidence: 99%

Simple physics of the partly pinned fluid systems

Krakoviack

2014

The Journal of Chemical Physics

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In this paper, we consider some aspects of the physics of the partly pinned (PP) systems obtained by freezing in place particles in equilibrium bulk fluid configurations in the normal (nonglassy) state. We first discuss the configurational overlap and the disconnected density correlation functions, both in the homogeneous and heterogeneous cases, using the tools of the theory of adsorption in disordered porous solids. The relevant Ornstein-Zernike equations are derived, and asymptotic results valid in the regime where the perturbation due to the pinning process is small are obtained. Second, we consider the homogeneous PP lattice gas as a means to make contact between pinning processes in particle and spin systems and show that it can be straightforwardly mapped onto a random field Ising model with a strongly asymmetric bimodal distribution of the field. Possible implications of these results for studies of the glass transition based on PP systems are also discussed.

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Concentration and mass dependence of transport coefficients and correlation functions in binary mixtures with high mass asymmetry

Cited by 17 publications

References 41 publications

Nature of intrinsic uncertainties in equilibrium molecular dynamics estimation of shear viscosity for simple and complex fluids

Nature of intrinsic uncertainties in equilibrium molecular dynamics estimation of shear viscosity for simple and complex fluids

Mode-coupling theory predictions for the dynamical transitions of partly pinned fluid systems

Simple physics of the partly pinned fluid systems

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