Five-fold symmetry as indicator of dynamic arrest in metallic glass-forming liquids.

Y C Hu,F X Li,W H Wang,M Z Li,H Y Bai

doi:10.1038/ncomms9310

Abstract

With sufficient high cooling rates, a variety of liquids, including metallic melts, will cross a glass transition temperature and solidify into glass accompanying a marked increase of the shear viscosity in approximately 17 orders of magnitude. Because of the intricate atomic structure and dynamic behaviours of liquid, it is yet difficult to capture the underlying structural mechanism responsible for the marked slowing down during glass transition, which impedes deep understanding of the formation and nature of glasses. Here, we report that a universal structural indicator, the average degree of five-fold local symmetry, can well describe the slowdown dynamics during glass transition. A straightforward relationship between structural parameter and viscosity (or α-relaxation time) is introduced to connect the dynamic arrest and the underlying structural evolution. This finding would be helpful in understanding the long-standing challenges of glass transition mechanism in the structural perspective.

Highlights

With sufficient high cooling rates, a variety of liquids, including metallic melts, will cross a glass transition temperature and solidify into glass accompanying a marked increase of the shear viscosity in approximately 17 orders of magnitude
We show that the parameter W can depict the marked arrest in metallic glasses (MGs)-forming liquids, and a straightforward relationship between the proposed structural parameter and the drastic dynamic arrest as well as the underlying structural evolution for the metallic liquids is deduced
The crystalline structures are formed without five-fold symmetry, whereas in vitrification crystallization is suppressed and glassy states are obtained with local structures containing both icosahedral-like and fcc-like structural features[15,44]

Summary

Introduction

With sufficient high cooling rates, a variety of liquids, including metallic melts, will cross a glass transition temperature and solidify into glass accompanying a marked increase of the shear viscosity in approximately 17 orders of magnitude. A straightforward relationship between structural parameter and viscosity (or a-relaxation time) is introduced to connect the dynamic arrest and the underlying structural evolution This finding would be helpful in understanding the long-standing challenges of glass transition mechanism in the structural perspective. The five-fold symmetry is verified to play a crucial role in dynamical arrest in colloidal and granular systems[12,13] and closely correlated with some properties such as fragility and boson peak[16,17]. This indicates that the five-fold symmetry may be a good structural parameter for establishing the structure–property relationship. It is essential to investigate the effect of the five-fold symmetry on the dynamics in MG-forming liquids

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Conclusion