Nonequilibrium Thermodynamics of Amorphous Materials II: Effective-Temperature Theory

TL;DR

This paper develops a theoretical framework for understanding the effective temperature in glass-forming materials under external forces, emphasizing the weak coupling between configurational and vibrational degrees of freedom during deformation.

Contribution

It introduces a new equation of motion for the effective temperature based on nonequilibrium thermodynamics, extending previous work to amorphous materials under external driving.

Findings

Derived an equation of motion for the effective temperature.

Showed how the effective temperature couples to system dynamics.

Provided a theoretical basis for nonequilibrium behavior in glasses.

Abstract

We develop a theory of the effective disorder temperature in glass-forming materials driven away from thermodynamic equilibrium by external forces. Our basic premise is that the slow configurational degrees of freedom of such materials are weakly coupled to the fast kinetic/vibrational degrees of freedom, and therefore that these two subsystems can be described by different temperatures during deformation. We use results from the preceding paper on the nonequilibrium thermodynamics of systems with internal degrees of freedom to derive an equation of motion for the effective temperature and to learn how this temperature couples to the dynamics of the system as a whole.