Home – Home – Jornals – Avtometriya 2023 number 3

The presence of an medium-range order in glassy materials, i.e., structural correlations on the nanometer scale, leads to fluctuations of elastic constants with the same characteristic correlation radius. The question of what is the characteristic amplitude of these fluctuations is of great interest both from the applied point of view and from the point of view of fundamental understanding of the structure and dynamics of glassy materials. In this study, we find the value of mean-square fluctuations of the shear modulus at the nanometer scale in salol (phenyl salicylate) molecular glass and its dependence on temperature during glass melting into a supercooled liquid. For this purpose, we use the theory of elasticity in a medium with spatial fluctuations of elastic constants in calculating the phonon free path using the perturbation theory. In addition, in the supercooled state of the material, we take into account the contribution of structure relaxation to phonon damping. Using the Ioffe-Regel criterion for the localization of transverse phonons, we find a relationship between the magnitude of shear modulus fluctuations and the frequency of the so-called boson peak caused by them in the spectrum of vibrational excitations of glasses. We determine this frequency from experimental data on the spectra of low-frequency inelastic light scattering in salol. A comparison with the theory makes it possible to find the temperature dependence of the rms fluctuations of the shear modulus at the nanometer scale. In addition, we compare this dependence with the temperature behavior of the Landau-Placzek parameter in salol. We also determine the temperature dependence of the radius of structural correlations in salol and glycerol and compare it with the temperature dependence of the size of the dynamic inhomogeneity.