Role of Microscopic Stress Fluctuations in Glass Transition and Glass Formation

Abstract

AbstractAlthough the structure of liquids and glasses may appear highly disordered, the atomic motions in these phases are rather strongly correlated. Such a correlation, however, cannot be readily described by a pair density function, and higher order correlation functions are necessary. We suggest that the microscopic stresses defined at each atom are quite useful in describing such high order correlations. We discuss how the concept of the microscopic stress fluctuation helps to describe and understand the glass transition and glass formation phenomena. In a molecular dynamics study the local shear stresses were found to become orientationally correlated below a transition temperature, Ts, which is close to the melting temperature. Below Ts the viscosity shows a rapid increase and transverse phonons become more stable. Thus Ts could be viewed as a dynamical glass transition temperature. The conventional glass transition can be described in terms of the elastic percolation of the orientationally correlated regions. On the other hand, the microscopic stresses in the crystalline solid solutions define the topological stability limit of the crystalline phase, and predict the minimum solute concentration to form stable amorphous alloys.