Fickian Non-Gaussian Diffusion in Glass-Forming Liquids

Rusciano, Francesco; Pastore, Raffaele; Greco, Francesco

doi:10.1103/physrevlett.128.168001

Cited by 37 publications

(43 citation statements)

References 53 publications

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“…This result suggests that the Gaussian approximation for G(x; t) may not be appropriate for the timescale over which O 2 diffuses the lengths of colloidal CSH or the capillary pore. Our result is reasonable since non-Gaussian distributions, in fact, have been frequently observed at the microscopic scale in various heterogeneous systems such as confined water in CSH [90], glass-forming liquids [25], or colloidal suspensions [26,27].…”

Section: Application Of 2sfd Model To Gas O 2 In Cement Pastesupporting

confidence: 83%

“…A microstructure of cementitious materials inherently exhibits a heterogeneous composition, which can result in the non-Gaussian diffusion of gases. To effectively describe the diffusion in heterogeneous material, the concept of fluctuating diffusivity (FD) [18,19,20,21,22,23,24] has been demonstrated to be useful, as evidenced by the studies for the glass forming liquid [25], colloidal suspensions [26,27], and biological systems [28,29]. The diffusion of a free molecule with fluctuating diffusivity is described by the equation…”

Section: Introductionmentioning

confidence: 99%

“…Figure3: The trajectory of O 2 over the observed time duration 1000/(r f + rs) at a porosity φ = 0.5 is represented by the pink curve. For comparison, the trajectory of particle diffusion with a constant diffusion coefficient, as represented by equation(25), is depicted by the blue curve. Closed circle symbols are also displayed at the same time intervals of (r f + rs) −1 .…”

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confidence: 99%

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Gas Diffusion in Cement Pastes: An Analysis using a Fluctuating Diffusivity Model

Nakai¹,

Ishida²

2023

Preprint

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This work propose an application of the concept of fluctuating diffusivity to the diffusion of gas molecules in cementitious materials, particularly through a two-state fluctuating diffusivity (2SFD) model. The 2SFD model is utilized to investigate the diffusion of oxygen in cement pastes. The analysis provides a reasonable description of the diffusion coefficient of oxygen in cement pastes, and highlights the presence of non-Gaussian diffusion, which can be attributed to the heterogeneous microstructure. The presence of non-Gaussianity in the probability density of the molecule's displacement, characterized by heavier tails than those of the Gaussian distribution, may have a significant impact on the durability assessments of concrete structures.

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Section: Application Of 2sfd Model To Gas O 2 In Cement Pastesupporting

confidence: 83%

Section: Introductionmentioning

confidence: 99%

mentioning

confidence: 99%

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Gas Diffusion in Cement Pastes: An Analysis using a Fluctuating Diffusivity Model

Nakai¹,

Ishida²

2023

Preprint

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“…It is interesting to note that some deviation persists although the MSD data show a nearly diffusive behavior at long time. Actually, diffusive behavior does not guarantee that the self-part of the van Hove functions are purely Gaussian, MSD data being average quantities over several modes of motion involving dynamical heterogeneities. − …”

Section: Resultsmentioning

confidence: 99%

Microscopic Dynamics and Viscoelasticity of Vitrimers

et al. 2022

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We implement a hybrid molecular dynamics/Monte Carlo simulation to study the microscopic dynamics and the macroscopic rheology of vitrimers with a fast bond exchange rate. We show that the linear viscoelastic properties and mean squared displacement of the vitrimers collapse onto master curves by applying the same shift factors that follow the Williams−Landel−Ferry equation at low temperatures and Arrhenius-like behavior at high temperatures. The linkage between the microscopic dynamics and the linear rheology of vitrimers is established using the generalized Stokes−Einstein relationship, which efficiently extends the timescale of simulations and predicts the viscoelasticity. The values of the shift factors are related to the characteristic decay time of the intermediate scattering function, which is accessible in scattering experiments. The same results hold in the case of an all-atom model of an ionic liquid. Our methodology provides a microscopic basis for the time-superposition principle and predicts the macroscopic rheology of thermo-rheologically simple vitrimers.

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“…Such decay of the PDF is termed Laplace tails [31]. Notable examples include colloidal beads in heterogeneous optical force field [32], zooplanktons under crowding [33], glass-forming liquids [34], nanoparticles in polymer melts [35], motion of particles at liquid-solid interface [36], particle displacements close to glass and jamming transitions [37,38] etc. In [39] it was suggested that there might exist a universal convergence to the Laplace tails.…”

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confidence: 99%

Universal to Non-Universal Transition of the statistics of Rare Events During the Spread of Random Walks

Singh¹,

Burov²

2023

Preprint

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Particle hopping is a common feature in heterogeneous media. We explore such motion by using the widely applicable formalism of the continuous time random walk and focus on the statistics of rare events. Numerous experiments have shown that the decay of the positional probability density function P (X, t), describing the statistics of rare events, exhibits universal exponential decay. We show that such universality ceases to exist once the threshold of exponential distribution of particle hops is crossed. While the mean hop is not diverging and can attain a finite value; the transition itself is critical. The exponential universality of rare events arises due to the contribution of all the different states occupied during the process. Once the reported threshold is crossed, a single large event determines the statistics. In this realm, the big jump principle replaces the large deviation principle, and the spatial part of the decay is unaffected by the temporal properties of rare events.

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Fickian Non-Gaussian Diffusion in Glass-Forming Liquids

Cited by 37 publications

References 53 publications

Gas Diffusion in Cement Pastes: An Analysis using a Fluctuating Diffusivity Model

Gas Diffusion in Cement Pastes: An Analysis using a Fluctuating Diffusivity Model

Microscopic Dynamics and Viscoelasticity of Vitrimers

Universal to Non-Universal Transition of the statistics of Rare Events During the Spread of Random Walks

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