Sound absorption in glasses

Buchenau, U.; D’Angelo, Giovanna; Carini, G.; Liu, X.; Ramos, Miguel

doi:10.48550/arxiv.2012.10139

Cited by 4 publications

(5 citation statements)

References 80 publications

(236 reference statements)

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“…A third alternative is that secondary relaxation is caused by a slow degree of freedom (say, some intra-molecular motion) that is distinct from the ones contributing to the α-peak, which then raises further questions about the inter-relation between these processes. Previous work also tried to identify how universal the shape of the excess signal can be depending on experimental probes [24,25], the type of molecules [22,26], and thermodynamic conditions (by, say, varying pressure [5]).…”

Section: *Equal Contributionsmentioning

confidence: 99%

Excess wings and asymmetric relaxation spectra in a facilitated trap model

Scalliet,

Guiselin,

Berthier

2021

Preprint

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In a recent computer study, we have shown that the combination of spatially heterogeneous dynamics and kinetic facilitation provides a microscopic explanation for the emergence of excess wings in deeply supercooled liquids. Motivated by these findings, we construct a minimal empirical model to describe this physics and introduce dynamic facilitation in the trap model, which was initially developed to capture the thermally-activated dynamics of glassy systems. We fully characterise the relaxation dynamics of this facilitated trap model varying the functional form of energy distributions and the strength of dynamic facilitation, combining numerical results and analytic arguments. Dynamic facilitation generically accelerates the relaxation of the deepest traps, thus making relaxation spectra strongly asymmetric, with an apparent "excess" signal at high frequencies. For well-chosen values of the parameters, the obtained spectra mimic experimental results for organic liquids displaying an excess wing. Overall, our results identify the minimal physical ingredients needed to describe excess processes in relaxation spectra of supercooled liquids.

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Section: *Equal Contributionsmentioning

confidence: 99%

Excess wings and asymmetric relaxation spectra in a facilitated trap model

Scalliet,

Guiselin,

Berthier

2021

Preprint

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“…The low temperature glass anomalies are well described by the soft potential model [12][13][14], an extension of the tunneling model [15] to include soft vibrations and low barrier relaxations. New numerical results confirm three soft potential model predictions, namely the existence of * Electronic address: buchenau-juelich@t-online.de a strong fourth order term in the mode potential [16], a density of soft vibrational modes increasing with the fourth power of their frequency [16][17][18][19][20], and a density of low barrier relaxations increasing proportional to the power 1/4 of the barrier height [21].…”

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confidence: 95%

“…Fig. 2 makes the connection to the soft potential model [12][13][14], where all soft modes have the same fourth order term in the mode potential E(A) as a function of the normal coordinate A. The mode is soft because the negative contribution to the restoring force from the unstable core potential (the continuous line in Fig.…”

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confidence: 99%

A note on Kauzmann's paradox

Buchenau¹

2021

Preprint

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“…In glasses [9], upon going to higher wavevectors, a crossover from ∼k 2 to a ∼k 4 regime is typically observed experimentally [10], where the ∼k 4 scaling has been interpreted as Rayleigh-type scattering from random fluctuations of some (usually macroscopic) quantity. In this sense, the heterogeneous elasticity theory (HET) has provided a derivation of this Rayleigh type damping based on the assumption of Gaussian spatial fluctuations of the shear modulus [11].…”

Section: Introductionmentioning

confidence: 99%

Theory of sound attenuation in amorphous solids from nonaffine motions

Baggioli

Zaccone

2022

J. Phys.: Condens. Matter

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We present a theoretical derivation of acoustic phonon damping in amorphous solids based on the nonaffine response formalism for the viscoelasticity of amorphous solids. The analytical theory takes into account the nonaffine displacements in transverse waves and is able to predict both the ubiquitous low-energy diffusive damping $\sim k^{2}$, as well as a novel contribution to the Rayleigh damping $\sim k^{4}$ at higher wavevectors and the crossover between the two regimes observed experimentally. The coefficient of the diffusive term is proportional to the microscopic viscous (Langevin-type) damping in particle motion (which arises from anharmonicity), and to the nonaffine correction to the static shear modulus, whereas the Rayleigh damping emerges in the limit of low anharmonicity, consistent with previous observations and macroscopic models. Importantly, the $k^4$ Rayleigh contribution derived here does not arise from harmonic disorder or elastic heterogeneity effects and it is the dominant mechanism for sound attenuation in amorphous solids as recently suggested by molecular simulations.

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Sound absorption in glasses

Cited by 4 publications

References 80 publications

Excess wings and asymmetric relaxation spectra in a facilitated trap model

Excess wings and asymmetric relaxation spectra in a facilitated trap model

A note on Kauzmann's paradox

Theory of sound attenuation in amorphous solids from nonaffine motions

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