A stress relaxation approach to glass transition

We propose that the onset of a glass transition can be defined as the point at which a supercooled liquid acquires the stress relaxation mechanism of a solid glass. We translate this condition into the rate equation for local relaxation events. This equation simultaneously gives two main signatures of a glass transition: stretched-exponential relaxation and the Vogel–Fulcher law. In the proposed picture, the increase of non-exponentiality of relaxation and deviation from the Arrhenius law both originate from the lag behind the new equilibrium state, to which the system is driven by external perturbation. This lag can be quantified by the number of local relaxation events, and we propose that this number is related to the system's fragility. The proposed theory reproduces several general correlations, including the correlation of fragility with non-exponentiality of relaxation and bonding type