Selenium glass transition: A model based on the enthalpy landscape approach and nonequilibrium statistical mechanics

We present a statistical model of the selenium glass transition based on the enthalpy landscape approach and nonequilibrium statistical mechanics. The model offers predictive calculation of the macroscopic properties of a glass-forming system, accounting for the effects of both composition and thermal history. In particular, we compute volume-temperature diagrams for selenium, starting from the equilibrium liquid state and cooling through the glass transition regime. We show excellent agreement between the computed molar volume and thermal expansion coefficient of selenium glass and those measured experimentally by Varshneya and co-workers. Since the model implementation is not limited by time scale, we can achieve realistic cooling rates not accessible to standard molecular simulations. To demonstrate the versatility of our modeling approach, we compute the molar volume of selenium glass with cooling rates ranging from 10-12 to 1012 K/s. The model can also capture thermal compaction (hysteresis) behavior upon subsequent heat treatment of the initially cooled glass. Finally, we present a technique for computation of shear viscosity at and below the glass transition range and apply this technique to selenium. This technique also enables calculation of the fragility of a supercooled liquid.