The Experts below are selected from a list of 14340 Experts worldwide ranked by ideXlab platform

Matthieu Wyart - One of the best experts on this subject based on the ideXlab platform.

  • effects of coordination and pressure on Sound Attenuation boson peak and elasticity in amorphous solids
    Soft Matter, 2014
    Co-Authors: Eric Degiuli, Adrien Laversannefinot, Gustavo During, Edan Lerner, Matthieu Wyart
    Abstract:

    Connectedness and applied stress strongly affect elasticity in solids. In various amorphous materials, mechanical stability can be lost either by reducing connectedness or by increasing pressure. We present an effective medium theory of elasticity that extends previous approaches by incorporating the effect of compression, of amplitude e, allowing one to describe quantitative features of Sound propagation, transport, the boson peak, and elastic moduli near the elastic instability occurring at a compression ec. The theory disentangles several frequencies characterizing the vibrational spectrum: the onset frequency where strongly-scattered modes appear in the vibrational spectrum, the pressure-independent frequency ω* where the density of states displays a plateau, the boson peak frequency ωBP found to scale as , and the Ioffe–Regel frequency ωIR where scattering length and wavelength become equal. We predict that Sound Attenuation crosses over from ω4 to ω2 behaviour at ω0, consistent with observations in glasses. We predict that a frequency-dependent length scale ls(ω) and speed of Sound ν(ω) characterize vibrational modes, and could be extracted from scattering data. One key result is the prediction of a flat diffusivity above ω0, in agreement with previously unexplained observations. We find that the shear modulus does not vanish at the elastic instability, but drops by a factor of 2. We check our predictions in packings of soft particles and study the case of covalent networks and silica, for which we predict ωIR ≈ ωBP. Overall, our approach unifies Sound Attenuation, transport and length scales entering elasticity in a single framework where disorder is not the main parameter controlling the boson peak, in agreement with observations. This framework leads to a phase diagram where various glasses can be placed, connecting microscopic structure to vibrational properties.

  • effects of coordination and pressure on Sound Attenuation boson peak and elasticity in amorphous solids
    arXiv: Soft Condensed Matter, 2014
    Co-Authors: Eric Degiuli, Adrien Laversannefinot, Gustavo During, Edan Lerner, Matthieu Wyart
    Abstract:

    Connectedness and applied stress strongly affect elasticity in solids. In various amorphous solids, mechanical stability can be lost either by reducing connectedness or by increasing pressure. We present an effective medium theory of elasticity that extends previous approaches by incorporating the effect of compression, of amplitude $e$, allowing one to describe quantitative features of Sound propagation, transport, the boson peak, and elastic moduli near the elastic instability occurring at a compression $e_c$. The theory disentangles several frequencies characterizing the vibrational spectrum: the onset frequency $\omega_0\sim \sqrt{e_c-e}$ where strongly-scattered modes appear in the vibrational spectrum, the pressure-independent frequency $\omega_*$ where the density of states displays a plateau, the boson peak frequency $\omega_{BP}$, and the Ioffe-Regel frequency $\omega_{IR}$ where scattering length and wavelength become equal. We predict that Sound Attenuation crosses over from $\omega^4$ to $\omega^2$ behaviour at $\omega_0$. We predict that a frequency-dependent length scale $l_s(\omega)$ and speed of Sound $\nu(\omega)$ characterize vibrational modes, and could be extracted from scattering data. One key result is the prediction of a flat diffusivity above $\omega_0$, in agreement with previously unexplained observations. We find that the shear modulus does not vanish at the elastic instability, but drops by a factor of 2. We check our predictions in packings of soft particles and study the case of covalent networks and silica. Overall, our approach unifies Sound Attenuation, transport and length scales entering elasticity in a single framework where disorder is not the main parameter controlling the boson peak, in agreement with observations. This framework leads to a phase diagram where various glasses can be placed, connecting microscopic structure to vibrational properties.

Alessia Marruzzo - One of the best experts on this subject based on the ideXlab platform.

  • heterogeneous shear elasticity of glasses the origin of the boson peak
    Scientific Reports, 2013
    Co-Authors: Alessia Marruzzo, Andrea Fratalocchi, Walter Schirmacher, Giancarlo Ruocco
    Abstract:

    The local elasticity of glasses is known to be inhomogeneous on a microscopic scale compared to that of crystalline materials. Their vibrational spectrum strongly deviates from that expected from Debye's elasticity theory: The density of states deviates from Debye's law, the Sound velocity shows a negative dispersion in the boson-peak frequency regime and there is a strong increase of the Sound Attenuation near the boson-peak frequency. By comparing a mean-field theory of shear-elastic heterogeneity with a large-scale simulation of a soft-sphere glass we demonstrate that the observed anomalies in glasses are caused by elastic heterogeneity. By observing that the macroscopic bulk modulus is frequency independent we show that the boson-peak-related vibrational anomalies are predominantly due to the spatially fluctuating microscopic shear stresses. It is demonstrated that the boson-peak arises from the steep increase of the Sound Attenuation at a frequency which marks the transition from wave-like excitations to disorder-dominated ones.

Giancarlo Ruocco - One of the best experts on this subject based on the ideXlab platform.

  • heterogeneous shear elasticity of glasses the origin of the boson peak
    Scientific Reports, 2013
    Co-Authors: Alessia Marruzzo, Andrea Fratalocchi, Walter Schirmacher, Giancarlo Ruocco
    Abstract:

    The local elasticity of glasses is known to be inhomogeneous on a microscopic scale compared to that of crystalline materials. Their vibrational spectrum strongly deviates from that expected from Debye's elasticity theory: The density of states deviates from Debye's law, the Sound velocity shows a negative dispersion in the boson-peak frequency regime and there is a strong increase of the Sound Attenuation near the boson-peak frequency. By comparing a mean-field theory of shear-elastic heterogeneity with a large-scale simulation of a soft-sphere glass we demonstrate that the observed anomalies in glasses are caused by elastic heterogeneity. By observing that the macroscopic bulk modulus is frequency independent we show that the boson-peak-related vibrational anomalies are predominantly due to the spatially fluctuating microscopic shear stresses. It is demonstrated that the boson-peak arises from the steep increase of the Sound Attenuation at a frequency which marks the transition from wave-like excitations to disorder-dominated ones.

Eric Degiuli - One of the best experts on this subject based on the ideXlab platform.

  • effects of coordination and pressure on Sound Attenuation boson peak and elasticity in amorphous solids
    Soft Matter, 2014
    Co-Authors: Eric Degiuli, Adrien Laversannefinot, Gustavo During, Edan Lerner, Matthieu Wyart
    Abstract:

    Connectedness and applied stress strongly affect elasticity in solids. In various amorphous materials, mechanical stability can be lost either by reducing connectedness or by increasing pressure. We present an effective medium theory of elasticity that extends previous approaches by incorporating the effect of compression, of amplitude e, allowing one to describe quantitative features of Sound propagation, transport, the boson peak, and elastic moduli near the elastic instability occurring at a compression ec. The theory disentangles several frequencies characterizing the vibrational spectrum: the onset frequency where strongly-scattered modes appear in the vibrational spectrum, the pressure-independent frequency ω* where the density of states displays a plateau, the boson peak frequency ωBP found to scale as , and the Ioffe–Regel frequency ωIR where scattering length and wavelength become equal. We predict that Sound Attenuation crosses over from ω4 to ω2 behaviour at ω0, consistent with observations in glasses. We predict that a frequency-dependent length scale ls(ω) and speed of Sound ν(ω) characterize vibrational modes, and could be extracted from scattering data. One key result is the prediction of a flat diffusivity above ω0, in agreement with previously unexplained observations. We find that the shear modulus does not vanish at the elastic instability, but drops by a factor of 2. We check our predictions in packings of soft particles and study the case of covalent networks and silica, for which we predict ωIR ≈ ωBP. Overall, our approach unifies Sound Attenuation, transport and length scales entering elasticity in a single framework where disorder is not the main parameter controlling the boson peak, in agreement with observations. This framework leads to a phase diagram where various glasses can be placed, connecting microscopic structure to vibrational properties.

  • effects of coordination and pressure on Sound Attenuation boson peak and elasticity in amorphous solids
    arXiv: Soft Condensed Matter, 2014
    Co-Authors: Eric Degiuli, Adrien Laversannefinot, Gustavo During, Edan Lerner, Matthieu Wyart
    Abstract:

    Connectedness and applied stress strongly affect elasticity in solids. In various amorphous solids, mechanical stability can be lost either by reducing connectedness or by increasing pressure. We present an effective medium theory of elasticity that extends previous approaches by incorporating the effect of compression, of amplitude $e$, allowing one to describe quantitative features of Sound propagation, transport, the boson peak, and elastic moduli near the elastic instability occurring at a compression $e_c$. The theory disentangles several frequencies characterizing the vibrational spectrum: the onset frequency $\omega_0\sim \sqrt{e_c-e}$ where strongly-scattered modes appear in the vibrational spectrum, the pressure-independent frequency $\omega_*$ where the density of states displays a plateau, the boson peak frequency $\omega_{BP}$, and the Ioffe-Regel frequency $\omega_{IR}$ where scattering length and wavelength become equal. We predict that Sound Attenuation crosses over from $\omega^4$ to $\omega^2$ behaviour at $\omega_0$. We predict that a frequency-dependent length scale $l_s(\omega)$ and speed of Sound $\nu(\omega)$ characterize vibrational modes, and could be extracted from scattering data. One key result is the prediction of a flat diffusivity above $\omega_0$, in agreement with previously unexplained observations. We find that the shear modulus does not vanish at the elastic instability, but drops by a factor of 2. We check our predictions in packings of soft particles and study the case of covalent networks and silica. Overall, our approach unifies Sound Attenuation, transport and length scales entering elasticity in a single framework where disorder is not the main parameter controlling the boson peak, in agreement with observations. This framework leads to a phase diagram where various glasses can be placed, connecting microscopic structure to vibrational properties.

Walter Schirmacher - One of the best experts on this subject based on the ideXlab platform.

  • heterogeneous shear elasticity of glasses the origin of the boson peak
    Scientific Reports, 2013
    Co-Authors: Alessia Marruzzo, Andrea Fratalocchi, Walter Schirmacher, Giancarlo Ruocco
    Abstract:

    The local elasticity of glasses is known to be inhomogeneous on a microscopic scale compared to that of crystalline materials. Their vibrational spectrum strongly deviates from that expected from Debye's elasticity theory: The density of states deviates from Debye's law, the Sound velocity shows a negative dispersion in the boson-peak frequency regime and there is a strong increase of the Sound Attenuation near the boson-peak frequency. By comparing a mean-field theory of shear-elastic heterogeneity with a large-scale simulation of a soft-sphere glass we demonstrate that the observed anomalies in glasses are caused by elastic heterogeneity. By observing that the macroscopic bulk modulus is frequency independent we show that the boson-peak-related vibrational anomalies are predominantly due to the spatially fluctuating microscopic shear stresses. It is demonstrated that the boson-peak arises from the steep increase of the Sound Attenuation at a frequency which marks the transition from wave-like excitations to disorder-dominated ones.