Modified elastic model for viscosity in glass-forming systems

For most glass-forming liquids, the temperature dependence of viscosity is non-Arrhenius. Despite the technological and geological importance, the origin of this non-Arrhenius temperature dependence of viscosity remains elusive to date and constitutes an important but unsolved problem in condensed-matter physics. It has become increasingly clear in recent years that high-temperature elasticity and viscosity of glass-forming liquids are strongly correlated. This work proposes a modified elastic model to predict equilibrium viscosity of glass-forming liquids. The modified elastic model considers the configurational entropy as a factor controlling the activation energy for viscous flow in addition to the high-frequency shear modulus as in the Dyre shoving model. It works much better than the shoving model in fitting equilibrium viscosity for both strong and fragile systems. The modified model also has the capability to estimate the nonequilibrium isostructural viscosity of glass from the equilibrium viscosity and the temperature-dependent elasticity of the glassy state.