Relationship between the boson peak and first sharp diffraction peak in glasses

TL;DR

This study quantitatively links the boson peak dynamics in glasses to medium-range structural order, revealing that the first sharp diffraction peak determines elastic heterogeneity size, which influences BP characteristics.

Contribution

It introduces a quantitative relationship between the boson peak and medium-range order in glasses using heterogeneous elasticity theory.

Findings

Strong correlation between FSDP wavenumber and BP determinants

FSDP size influences elastic modulus heterogeneity

Elastic modulus fluctuations determine BP frequency and intensity

Abstract

Boson peak (BP) dynamics refers to the universal excitation in the terahertz region of glass. In this study, the universal dynamics of BP were quantitatively evaluated in various glassy materials based on the heterogeneous elasticity theory (HET), and the determinants of BP were successfully extracted. A strong correlation was observed between the maximum possible coarse-graining wavenumber, which is a determinant of the BP in the HET, and the first sharp diffraction peak (FSDP) wavenumber, which is a characteristic index of the medium-range order in glasses. The results indicate that the behaviour of BP in glass can be quantitatively understood in the following two steps. First, the FSDP representing the largest structural correlation in glass is dominantly used to determine the unit size of the elastic modulus heterogeneity, and second, the magnitude of the elastic modulus fluctuation is used to determine the frequency and intensity of the BP.