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Elastic anomalies in glasses: Elastic string theory understanding of the cases of glycerol and silica

机译：眼镜的弹性异常：弹性弦理论对甘油和二氧化硅病例的理解了解

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In this work we present an implementation of the analytical string theory recently applied to the description of glasses. These are modeled as continuum media with embedded elastic string heterogeneities, randomly located and randomly oriented, which oscillate around a straight equilibrium position with a fundamental frequency depending on their length. The existence of a length distribution is reflected then in a distribution of oscillation frequencies which is responsible for the boson peak in the glass density of states. Previously, it has been shown that such a description can account for the elastic anomalies reported at frequencies comparable with the boson peak: the strong phonon scattering and the negative dispersion in the sound velocity, as a result of the interference of the string oscillations with propagating sound plane waves. Here we start from the generalized hydrodynamics to determine the dynamic correlation function S(k, ω) associated with the coherent, dispersive, and attenuated sound waves resulting from such interference. We show that once the vibrational density of states has been measured, we can use it for unambiguously fixing the string length distribution inherent to a given glass. The density-density correlation function obtained using such distribution is strongly constrained, and able to account for the experimental data collected on two prototypical glasses with very different microscopic structure and fragility: glycerol and silica. The obtained string length distribution is compatible with the typical size of elastic heterogeneities previously reported for silica and supercooled liquids, and the atomic motion associated with the string dynamics is consistent with the soft modes recently identified in large-scale numerical simulations as nonphonon modes responsible for the boson peak. The theory is thus in agreement with the most recent advances in the understanding of the glass-specific dynamics and offers an appealing, simple understanding of the microscopic origin of the latter, while raising new questions on the universality or material specificity of the string distribution properties.
机译：在这项工作中，我们展示了最近应用于眼镜的描述的分析弦理论的实施。这些被建模为连续介质，其具有嵌入的弹性串异质性，随机定位和随机定向，这取决于它们的长度，基本频率围绕直线平衡位置振荡。然后反映了长度分布的存在，然后反映在振荡频率的分布中，该振荡频率负责状态的玻璃密度的玻色子峰。先前，已经表明，这种描述可以考虑在与玻色子峰相当的频率下报告的弹性异常：由于串振荡与传播的串振荡的干扰，强子散射和声速中的负分散。声波波浪。这里，我们从广义流体动力学开始，以确定与这种干扰产生的相干，分散和衰减声波相关联的动态相关函数S（k，ω）。我们表明，一旦测量了各州的振动密度，我们就可以使用它来明确地固定给定玻璃固有的弦长度分布。使用这种分布获得的密度密度相关函数受到强烈约束，并且能够考虑在两个具有非常不同的微观结构和脆性的原型玻璃上收集的实验数据：甘油和二氧化硅。所获得的弦长度分布与先前对二氧化硅和过冷液体报告的弹性异质件的典型尺寸兼容，与弦动力学相关的原子运动与最近在大规模数值模拟中识别的软模式一致，作为负责的非对应模式玻色峰。因此，该理论与最近的玻璃特定动态的最新进步一致，并提供了对后者的微观起源的吸引力，简单地理解，同时提高了弦代性或物质特异性的新问题。

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  • 来源
    《Physical review》 |2020年第17期|174311.1-174311.14|共14页
  • 作者

    Ernesto Bianchi; Valentina M. Giordano; Fernando Lund;

  • 作者单位

    Departamento de Fisica Facultad de Ciencias Fisicas y Matematicas Universidad de Chile Santiago Chile Instituto de Fisica Pontificia Universidad Catolica de Chile Casilla 306 Santiago Chile;

    Institut Lumiere Matiere UMR 5306 Universite Lyon 1-CNRS F-69622 Villeurbanne Cedex France;

    Departamento de Fisica Facultad de Ciencias Fisicas y Matematicas Universidad de Chile Santiago Chile CIMAT Facultad de Ciencias Fisicas y Malematicas Universidad de Chile Santiago Chile;

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