Abstract

The presence of the medium-range order in the glassy materials, i.e. structural correlations at the nanometer scales, leads to fluctuations of elastic constants with the same characteristic radius of correlations. The problem concerning the characteristic amplitude of these fluctuations is of great interest from both the application point of view and that of fundamental understanding of the structure and dynamics of glassy materials. In this work, the value of the nano-scale root-mean-square fluctuations of the shear modulus in the molecular glass salol (phenylsalicylate) and its dependence on temperature in the process of glass melting to a supercooled liquid are found. With this purpose, the theory of elasticity in the medium with spatial fluctuations of elastic constants is used when calculating the free path of phonons, according to perturbation theory. In addition, in the supercooled state of material, the contribution of the structure relaxation to phonon attenuation is considered. By using the Ioffe–Regel criterion for localization of transverse phonons, the relationship between the value of the shear modulus fluctuations and the frequency of the so-called boson peak induced by them in the spectrum of the vibrational excitations of glasses is found. This frequency is determined from the experimental data on the spectra of low-frequency inelastic light scattering in salol. Comparison with the theory makes it possible to find the temperature dependence of the value of nanoscale root-mean-square fluctuations of the shear modulus. In addition, this dependence is compared with the temperature behavior of the Landau–Placzek parameter in salol. The temperature dependence of the radius of structural correlations in salol and glycerine is also determined and compared with the temperature dependence of the size of the dynamic inhomogeneity.

中文翻译：

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非弹性光散射法测定萨洛尔剪切模量的均方根幅值

摘要

玻璃态材料中中程有序的存在，即纳米尺度的结构相关性，导致具有相同特征相关性半径的弹性常数的波动。从应用的角度以及对玻璃材料的结构和动力学的基本理解的角度来看，有关这些波动的特征幅度的问题都非常有趣。在这项工作中，发现了分子玻璃萨洛尔（水杨酸苯酯）中剪切模量的纳米级均方根波动值及其在玻璃熔化成过冷液体的过程中对温度的依赖性。为此，根据微扰理论，在计算声子的自由程时，使用具有弹性常数空间涨落的介质中的弹性理论。此外，在材料过冷状态下，还考虑了结构弛豫对声子衰减的贡献。通过使用横向声子局域化的 Ioffe-Regel 准则，找到了玻璃振动激励谱中剪切模量波动值与由它们引起的所谓玻色子峰频率之间的关系。该频率是根据萨洛尔低频非弹性光散射光谱的实验数据确定的。与理论的比较使得可以找到剪切模量的纳米级均方根波动值的温度依赖性。此外，还将这种依赖性与 salol 中的 Landau-Placzek 参数的温度行为进行了比较。还确定了萨洛尔和甘油中结构关联半径的温度依赖性，并将其与动态不均匀性大小的温度依赖性进行比较。