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 similar to k (2), as well as a novel contribution to the Rayleigh damping similar to 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.

Theory of sound attenuation in amorphous solids from nonaffine motions / M. Baggioli, A. Zaccone. - In: JOURNAL OF PHYSICS. CONDENSED MATTER. - ISSN 0953-8984. - 34:21(2022 May 24), pp. 215401.1-215401.10. [10.1088/1361-648X/ac5d8b]

Theory of sound attenuation in amorphous solids from nonaffine motions

A. Zaccone
Ultimo
2022

Abstract

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 similar to k (2), as well as a novel contribution to the Rayleigh damping similar to 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.
Rayleigh damping; amorphous solids; linear response theory; nonaffine elasticity; sound damping; waves in random media;
Settore FIS/03 - Fisica della Materia
Settore FIS/02 - Fisica Teorica, Modelli e Metodi Matematici
29-mar-2022
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Utilizza questo identificativo per citare o creare un link a questo documento: https://hdl.handle.net/2434/944593
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