CCMP Seminar Series: Dr. Cillian Cockrell
When: Tuesday, March 19, 2024, 2:00 PM - 3:00 PM
Where: G O Jones Building, Room 610, Mile End
Speaker: Dr. Cillian Cockrell
The Glass Transition
While the glass transition is easy to identify and reproduce macroscopically, the underlying atomic mechanisms which facilitate the transition from amorphous solid to fluid are still poorly understood.
We conduct classical molecular dynamics simulations on a variety of inorganic glasses in order to identify these mechanisms for the glass state in general. We find that the essential qualities which constitute a glass and its transition to a liquid are present even in systems containing only a few hundred atoms, while also modelling much larger systems. Atomic mobility, the ability of an atom to escape its local coordination environment, is identified as a universal marker of the glass transition. In the solid state, a negligible fraction of atoms is mobile, whereas in the liquid state, effectively all atoms are mobile. The glass transition is a continuous transition between these limiting states, with half of the network forming atoms attaining mobility exactly at the glass transition temperature over a specific mobility half life, informed by thermodynamics. Over time, however, network forming atoms which were immobile may swap to become mobile and vice versa. The overall population of mobile atoms remains at a half.