Absolutely necessary to consider the caged dynamics and the JGX β-relaxation in solving the glass transition problem

Ngai Ngai,S Capaccioli ,Hong Wang

doi:10.5488/cmp.22.43605

Abstract

The 2003 seminal paper entitled "Is the Fragility of a Liquid Embedded in the Properties of Its Glass?" by Tullio Scopigno, Giancarlo Ruocco, Francesco Sette, and Giulio Monaco, reported that the properties of the structural $\alpha$-relaxation of glass-formers are already present in the faster caged dynamics. Their important discovery has far-reaching implication of the processes faster than the structural $\alpha$-relaxation that cannot be ignored in solving the glass transition problem. Since then, experiments and simulations performed on many glass-formers with diverse chemical and physical structures have found strong connections of the $\alpha$-relaxation with not only the caged dynamics but also with the secondary relaxation of the special kind, called the JGX $\beta$-relaxation. The general results indicate that these fast processes are inseparable from the $\alpha$-relaxation, and any attempt to solve the glass transition problem should take account of this fact. Examples of the connections are given in this paper to elucidate the developments and advances made since the inspiring publication of Scopigno et al.

Highlights

Published in 2003, the paper “Is the Fragility of a Liquid Embedded in the Properties of Its Glass?”by Tullio Scopigno, Giancarlo Ruocco, Francesco Sette, and Giulio Monaco [1] is a landmark publication with impact on past and current research in dynamics and thermodynamics of glass-forming materials
They found that the inelastic x-ray scattering (IXS) data of f (Q, T) in the low Q limit at temperatures below the glass transition temperature Tg of many glass-formers can be well described by the functional form, f (Q → 0, T) = [1 + α(T/Tg)]−1, (1)
They found that the vibrational properties of the glass well below Tg correlate with the fragility index, which is a property of the cooperative α-relaxation of the viscous liquid at and above Tg

Summary

Introduction

Published in 2003, the paper “Is the Fragility of a Liquid Embedded in the Properties of Its Glass?”. By Tullio Scopigno, Giancarlo Ruocco, Francesco Sette, and Giulio Monaco [1] is a landmark publication with impact on past and current research in dynamics and thermodynamics of glass-forming materials. In this innovative research they used inelastic x-ray scattering (IXS) measurements of the dynamic structure factor to access the high frequency (terahertz) dynamical properties of glasses of different kinds. We present the other connections of the short time vibrational and secondary relaxation to the terminal α-relaxation developed over two decades, which magnify the impact

Supporting IXS data of SRSM by neutron scattering data and simulations

The JGX β-relaxation: the intermediary of caged dynamics and αrelaxation

Caged dynamics is terminated by the JGX β-relaxation

Summary and conclusions