Microscopic Theory for the Role of Attractive Forces in the Dynamics of Supercooled Liquids

Dell, Zachary E.; Schweizer, Kenneth S.

doi:10.1103/physrevlett.115.205702

Cited by 39 publications

(42 citation statements)

References 56 publications

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“…Explicit attractive forces are not taken into account dynamically, but they would serve to further slow down the mobile liquid particles near the surface. Treating the latter may require modifying the dynamic force vertex using the "projected dynamics theory" approach [71].…”

Section: Attractive Rough Wallsmentioning

confidence: 99%

Theory of the spatial transfer of interface-nucleated changes of dynamical constraints and its consequences in glass-forming films

Phan

Schweizer

2019

The Journal of Chemical Physics

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We formulate a new theory for how caging constraints in glass-forming liquids at a surface or interface are modified and then spatially transferred, in a layer-by-layer bootstrapped manner, into the film interior in the context of the dynamic free energy concept of the Nonlinear Langevin Equation (NLE) theory approach. The dynamic free energy at any mean location (cage center) involves contributions from two adjacent layers where confining forces are not the same. At the most fundamental level of the theory, the caging component of the dynamic free energy varies essentially exponentially with distance from the interface, saturating deep enough into the film with a correlation length of modest size and weak sensitivity to thermodynamic state. This imparts a roughly exponential spatial variation of all the key features of the dynamic free energy required to compute gradients of dynamical quantities including the localization length, jump distance, cage barrier, collective elastic barrier and alpha relaxation time. The spatial gradients are entirely of dynamical, not structural nor thermodynamic, origin. The theory is implemented for the hard sphere fluid and diverse interfaces which can be a vapor, a rough pinned particle solid, a vibrating (softened) pinned particle solid, or a smooth hard wall. Their basic description at the level of the spatially-heterogeneous dynamic free energy is identical, with the crucial difference arising from the first layer where dynamical constraints can be weaken, softened, or hardly changed depending on the specific interface. Numerical calculations establish the spatial dependence and fluid volume fraction sensitivity of the key dynamical property gradients for five different model interfaces. Comparison of the theoretical predictions for the dynamic localization length and glassy modulus with simulations and experiments for systems with a vapor interface reveal good agreement. The present advance sets the stage for using the Elastically Collective NLE theory to make quantitative predictions for the alpha relaxation time gradient, decoupling phenomena, Tg gradient, and many film-averaged properties of both model and experimental (colloids, molecules, polymers) systems with diverse interfaces and chemical makeup. arXiv:1901.01094v1 [cond-mat.soft]

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Section: Attractive Rough Wallsmentioning

confidence: 99%

Theory of the spatial transfer of interface-nucleated changes of dynamical constraints and its consequences in glass-forming films

Phan

Schweizer

2019

The Journal of Chemical Physics

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“…In principle, it is widely accepted that the dynamics of each material is ultimately related to its structure [13], and numerous theories have also aimed to exploit this idea to describe the glass transition [14][15][16][17][18][19][20][21][22]. Among these, mode-coupling theory (MCT) stands out as one of the few theories which is entirely based on first principles [8,19,20,23].…”

Section: Introductionmentioning

confidence: 99%

Multi-component generalized mode-coupling theory: predicting dynamics from structure in glassy mixtures

et al. 2021

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The emergence of glassy dynamics and the glass transition in dense disordered systems is still not fully understood theoretically. Mode-coupling theory (MCT) has shown to be effective in describing some of the non-trivial features of glass formation, but it cannot explain the full glassy phenomenology due to the strong approximations on which it is based. Generalized mode-coupling theory (GMCT) is a hierarchical extension of the theory, which is able to outclass MCT by carefully describing the dynamics of higher-order correlations in its generalized framework. Unfortunately, the theory has so far only been developed for single-component systems and as a result works poorly for highly polydisperse materials. In this paper, we solve this problem by developing GMCT for multi-component systems. We use it to predict the glassy dynamics of the binary Kob–Andersen Lennard-Jones mixture, as well as its purely repulsive Weeks–Chandler–Andersen analogue. Our results show that each additional level of the GMCT hierarchy gradually improves the predictive power of GMCT beyond its previous limit. This implies that our theory is able to harvest more information from the static correlations, thus being able to better understand the role of attraction in supercooled liquids from a first-principles perspective. Graphic abstract

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“…To capture the wide variation of fragility in polymer melts, non-universality was introduced motivated by the system-specific nature of the nm-scale conformational dynamics required for segmental hopping [8]. Good results have been demonstrated for T g , fragility and the temperature dependent segmental relaxation time.ECNLE theory has also been extended and applied to other problems: spatially heterogeneous relaxation in free standing thin films [9,10,11], segmental relaxation in polymer nanocomposites [12], attractive glass and gel formation in dense sticky colloidal suspensions [13], the effect of random pinning in dense liquids [14], penetrant diffusion in supercooled liquids and glasses [15,16], and activated relaxation in dynamically-asymmetric 2component mixtures [17].In this article, we revisit the basics of ECNLE theory of 1-component liquids to further establish it physical picture and address new questions. After a brief review of key technical aspects in section II, new numerical studies are presented in section III that explore a possible universality of the dynamic transient localization length, and alternative perspectives of the temperaturedependent barrier and effective volume fraction are also arXiv:1806.05348v1 [cond-mat.soft]…”

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confidence: 99%

Elastically Collective Nonlinear Langevin Equation Theory of Glass-Forming Liquids: Transient Localization, Thermodynamic Mapping, and Cooperativity

2018

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We analyze multiple new issues concerning activated relaxation in glassy hard sphere fluids and molecular and polymer liquids based on the elastically collective nonlinear Langevin equation (ECNLE) theory. By invoking a high-temperature reference state, a near universality of the apparent dynamic localization length scale is predicted for liquids of widely varying fragility, a result that is relevant to recent simulation studies and quasi-elastic neutron-scattering measurements. In contrast, in the same format, a strongly nonuniversal behavior is found for the activation barrier that controls long-time relaxation. Two measures of cooperativity in the ECNLE theory are analyzed. A particle-level total displacement associated with the alpha relaxation event is found to be only of order 1-2 particle diameters and weakly increases with cooling. In contrast, an alternative cooperativity length is defined as the spatial scale required to essentially recover the full barrier and bulk alpha time. This length scale grows strongly with cooling because of the emergence in the deeply supercooled regime of collective long-range elastic fluctuations required to allow local hopping. It becomes very large as the laboratory T is approached, though it is relatively modest at degrees of supercooling accessible with molecular dynamics simulation. The alpha time is found to be exponentially related to this cooperativity length over an enormous number of decades of relaxation time that span the lightly to deeply supercooled regimes. Moreover, the effective barrier height increases almost linearly with the growing cooperativity length scale. An alternative calculation of the collective elastic barrier based on a literal continuum mechanics approach is shown to result in very little change of the theoretical results for bulk properties but leads to a much smaller and less temperature-sensitive cooperativity length scale.

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Microscopic Theory for the Role of Attractive Forces in the Dynamics of Supercooled Liquids

Cited by 39 publications

References 56 publications

Theory of the spatial transfer of interface-nucleated changes of dynamical constraints and its consequences in glass-forming films

Theory of the spatial transfer of interface-nucleated changes of dynamical constraints and its consequences in glass-forming films

Multi-component generalized mode-coupling theory: predicting dynamics from structure in glassy mixtures

Elastically Collective Nonlinear Langevin Equation Theory of Glass-Forming Liquids: Transient Localization, Thermodynamic Mapping, and Cooperativity

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