Angell plot from the potential energy landscape perspective

Within the scenario of the potential energy landscape (PEL), a thermodynamic model has been developed to uncover the physics behind the Angell plot. In our model, by separating the barrier distribution in PELs into a Gaussian-like and a power-law form, we obtain a general relationship between the relaxation time and the temperature. The wide range of the experimental data in the Angell plot, as well as the molecular-dynamics data, can be excellently fitted by two characteristic parameters, the effective barrier (omega) and the effective width (sigma) of a Gaussian-like distribution. More importantly, the fitted omega and sigma 2 for all glasses are found to have a simple linear relationship within a very narrow band, and fragile and strong glasses are well separated in the omega-sigma 2 plot, which indicates that glassy states appear only in a specific region of the PEL.

Automated summary

By separating the barrier distribution in the potential energy landscape into Gaussian-like and power-law forms, researchers have found a general relationship between relaxation time and temperature, and discovered that glassy states only appear in a specific region of the landscape.