Many-Body Correlations Are Non-negligible in Both Fragile and Strong Glassformers

Luo, Chengjie; Robinson, Joshua F.; Pihlajamaa, Ilian; Debets, Vincent E.; Royall, C. Patrick; Janssen, Liesbeth M. C.

doi:10.1103/physrevlett.129.145501

Cited by 12 publications

(8 citation statements)

References 62 publications

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“…We note that S(0) is a primary measure of how fluid "structure" relates to its thermodynamic state and figures prominently in some models of glass formation, such as the mode-coupling theory. [39][40][41][42][43] We make some tentative suggestions for why some thermodynamic properties exhibit thermodynamic scaling, while this scaling property does not hold for other properties that might be expected to exhibit this property based on an assumed effective power-law intermolecular interaction potential. Thermodynamic scaling then offers some hints about the extraordinary interrelationships between the thermodynamics and dynamics of GF liquids.…”

Section: Introductionmentioning

confidence: 87%

“…Recent works have established the inadequacy of some more modern structurally based models of liquid dynamics, such as the mode-coupling theory, and other theories emphasizing the pair correlation function or averages of this quantity, providing molecular insights into the more abstract reasoning of Goldstein’s energy landscape arguments. Parenthetically, we note that there are recent promising works to include information about higher-order density correlations into a mode-coupling framework, which appears to lead to a much improved agreement between predictions and simulations, − but historically the fluid structure has often been identified with the readily observable pair correlation function or its Fourier transform, the static structure factor. Later, Goldstein suggested that the configurational entropy might occupy a place of primacy in this type of relationship after the development of the Adam–Gibbs (AG) model of glass formation, and he first formulated his highly influential energy landscape view of the dynamics of GF liquids as an elaboration of this reasoning .…”

Section: Introductionmentioning

confidence: 96%

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Thermodynamic–Dynamic Interrelations in Glass-Forming Polymer Fluids

Douglas

2022

Macromolecules

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There is a long history of trying to understand the dynamics of glass-forming and other condensed materials exhibiting highly anharmonic interparticle interactions, based on their thermodynamic properties. This has led to numerous correlations between thermodynamic (e.g., density, compressibility, enthalpy, entropy, and vapor pressure) and dynamic (e.g., viscosity, diffusion coefficients, and relaxation times) properties, and a steady stream of theoretical models has been introduced to rationalize these correlations in the absence of any generally accepted theory of the dynamics of non-crystalline condensed materials. We view the independent success of these various semi-empirical models of glass-forming liquids as possibly pointing to a greater unity arising from the strong interrelation between thermodynamic properties, which is a matter of interest beyond an understanding of the dynamics of glass-forming liquids. Accordingly, we utilize the lattice cluster theory (LCT) of polymer fluids to show that the configurational entropy, enthalpy, and internal energy are all closely interrelated, as suggested by recent measurements by Caruthers and Medvedev, so that the generalized entropy theory (GET) of glass formation, a combination of the LCT and Adam-Gibbs model, can be recast in terms of any of these thermodynamic properties as a matter of convenience. Thermodynamic scaling, a form of density-temperature scaling exhibited by dynamic and some thermodynamic properties, is used to assess which thermodynamic properties are most naturally linked to dynamics, and we explore the origin of this scaling by both direct calculations based on the GET and molecular dynamics simulations of a coarse-grained polymer model. Through a combination of our comprehensive modeling of thermodynamic properties using the LCT and the highly predictive GET model for how the fluid thermodynamics relate to its dynamics, along with simulation results confirming these theoretical frameworks, we obtain insights into thermodynamic aspects of collective motion and the slow β-relaxation processes of glass-forming liquids.

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Section: Introductionmentioning

confidence: 87%

Section: Introductionmentioning

confidence: 96%

Thermodynamic–Dynamic Interrelations in Glass-Forming Polymer Fluids

Douglas

2022

Macromolecules

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“…On the other hand, other properties, such as the low angle scattering intensity S (0) and G ∞ / k B T , do not exhibit thermodynamic scaling, where S (0) is related to the isothermal compressibility κ T , density ρ, and T through the definition, S (0) = ρ k B T κ T , appropriate in general for materials in equilibrium. We note that S (0) is a primary measure of how fluid “structure” relates to its thermodynamic state and figures prominently in some models of glass formation, such as the mode-coupling theory. − We make some tentative suggestions for why some thermodynamic properties exhibit thermodynamic scaling, while this scaling property does not hold for other properties that might be expected to exhibit this property based on an assumed effective power-law intermolecular interaction potential. Thermodynamic scaling then offers some hints about the extraordinary interrelationships between the thermodynamics and dynamics of GF liquids …”

Section: Introductionmentioning

confidence: 89%

Parallel Emergence of Rigidity and Collective Motion in a Family of Simulated Glass-Forming Polymer Fluids

Douglas

2023

Macromolecules

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The emergence of the solid state in glass-forming materials upon cooling is accompanied by changes in both thermodynamic and viscoelastic properties and by a precipitous drop in fluidity. Here, we investigate changes in basic elastic properties upon cooling in a family of simulated polymer fluids, as characterized by a number of stiffness measures, such as the “glassy plateau shear modulus” G p, the “non-ergodicity parameter” f s,q*, the bulk modulus B, the Poisson ratio ν, and the “Debye–Waller parameter” ⟨u 2⟩, where G p, f s,q*, and ⟨u 2⟩ correspond to the shear stress relaxation function G(t), the self-intermediate scattering function F s(q*, t), and the mean square displacement on a ps timescale, respectively. The time dependence of G(t) at elevated temperatures (T) resembles the power-law decay predicted by the Rouse model, but stress relaxation transitions to a stretched exponential form in the low-T liquid regime dominated by glassy segmental dynamics. In this “glassy dynamics” regime, the relaxation times from G(t) and F s(q*, t) closely track each other for all polymer models investigated, thereby justifying the identification of the α-relaxation time τα from F s(q*, t) with the structural relaxation time τ G from G(t). We show that τα can be expressed quantitatively both in terms of measures of the material “stiffness”, G p, and ⟨u 2⟩, and the extent L of cooperative particle exchange motion in the form of strings, establishing a direct relation between the growth of emergent elasticity and collective motion. Moreover, the macroscopic stiffness parameters, G p, B, and f s,q*, can all be expressed quantitatively in terms of the molecular scale stiffness parameter, k B T/⟨u 2⟩, with k B being Boltzmann’s constant, and we discuss the thermodynamic scaling of these properties. We also find that G p is related to the cohesive energy density ΠCED, pointing to the critical importance of attractive interactions in the elasticity and dynamics of glass-forming liquids. Finally, we discuss fluctuations in the local stiffness parameter as a quantitative measure of elastic heterogeneity and their significance for understanding both the linear and nonlinear elastic properties of glassy materials.

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“…for monodisperse systems where, following convention, we omit the superscript for the two-body structure factor and denote

. Although the convolution approximation for

is usually assumed to be reasonable for systems with relatively weak attracting interaction potentials ( 46 ), a recent mode-coupling theory study has revealed that including

can qualitatively change the glass transition diagram even for simple hard-sphere mixtures ( 54 ). Moreover, the convolution approximation provides even less accuracy for systems such as silica ( 46 ).…”

Section: Theory Of Liquid Structurementioning

confidence: 99%

Emergent structural correlations in dense liquids

Pihlajamaa

Luo

et al. 2023

PNAS Nexus

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The complete quantitative description of the structure of dense and supercooled liquids remains a notoriously difficult problem in statistical physics. Most studies to date focus solely on two-body structural correlations, and only a handful of papers have sought to consider additional three-body correlations. Here, we go beyond the state of the art by extracting many-body static structure factors from molecular dynamics simulations and by deriving accurate approximations up to the six-body structure factor via density functional theory. We find that supercooling manifestly increases four-body correlations, akin to the two- and three-body case. However, at small wave numbers, we observe that the four-point structure of a liquid drastically changes upon supercooling, both qualitatively and quantitatively, which is not the case in two-point structural correlations. This indicates that theories of the structure or dynamics of dense liquids should incorporate many-body correlations beyond the two-particle level to fully capture their intricate behavior.

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Many-Body Correlations Are Non-negligible in Both Fragile and Strong Glassformers

Cited by 12 publications

References 62 publications

Thermodynamic–Dynamic Interrelations in Glass-Forming Polymer Fluids

Thermodynamic–Dynamic Interrelations in Glass-Forming Polymer Fluids

Parallel Emergence of Rigidity and Collective Motion in a Family of Simulated Glass-Forming Polymer Fluids

Emergent structural correlations in dense liquids

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