Disorder classification of the vibrational spectra of modern glasses

Zhiwen Pan,Akio Koike,Gerhard Wilde,Omar Benzine,Lothar Wondraczek,Thomas D Bennett,Walter Schirmacher,Shigeki Sawamura,Rene Limbach

doi:10.1103/physrevb.104.134106

Abstract

Using the coherent-potential approximation in heterogeneous-elasticity theory with a log-normal distribution of elastic constants for the description of the Raman spectrum and the temperature dependence of the specific heat, we are able to reconstruct the vibrational density of states and characteristic descriptors of the elastic heterogeneity of a wide range of glassy materials. These descriptors are the nonaffine contribution to the shear modulus, the mean-square fluctuation of the local elasticity, and its correlation length. They enable a physical classification scheme for disorder in modern, industrially relevant glass materials. We apply our procedure to a broad range of real-world glass compositions, including metallic, oxide, chalcogenide, hybrid, and polymer glasses. Universal relationships between the descriptors on the one side, and the height and frequency position of the boson peak, the Poisson ratio and the liquid fragility index on the other side are established.

Highlights

IntroductionUsing the coherent-potential approximation in heterogeneous-elasticity theory with a log-normal distribution of elastic constants for the description of the Raman spectrum and the temperature dependence of the specific heat, we are able to reconstruct the vibrational density of states and characteristic descriptors of the elastic heterogeneity of a wide range of glassy materials
Zhiwen Pan,1 Omar Benzine,1 Shigeki Sawamura,2 Rene Limbach,1 Akio Koike,2 Thomas D
We use a mean-field theory which links the vibrational spectrum to the statistics of elastic heterogeneity, to characterize glasses according to their disorder strength and the characteristic correlation length of spatial elastic fluctuations

Summary

Introduction

Using the coherent-potential approximation in heterogeneous-elasticity theory with a log-normal distribution of elastic constants for the description of the Raman spectrum and the temperature dependence of the specific heat, we are able to reconstruct the vibrational density of states and characteristic descriptors of the elastic heterogeneity of a wide range of glassy materials These descriptors are the nonaffine contribution to the shear modulus, the mean-square fluctuation of the local elasticity, and its correlation length. We use a mean-field theory which links the vibrational spectrum to the statistics of elastic heterogeneity, to characterize glasses according to their disorder strength and the characteristic correlation length of spatial elastic fluctuations These descriptors are shown to be related to the elastic properties of the glass and the temperature dependence of the viscosity of the melt (“glass fragility”) and may be helpful for designing new materials for specific applications.

Results

Discussion

Conclusion