A glass is a type of amorphous solid whose structure is dominated by excluded-volume effects. Use this tag for questions about the glass transition and the thermodynamics and statistical mechanics of glasses.
When a liquid is cooled slowly, it normally undergoes a transition towards an ordered, crystalline phase at the temperature $T_f$ (freezing temperature).
However, if the rate of cooling is sufficiently rapid, the system can bypass crystallization and become an amorphous solid known as glass.
The glass transition temperature $T_g$ is less than the freezing temperature $T_f$ (as a rule of thumb, $T_g \simeq 0.66 T_f$), but its value depends on how exactly the cooling process is carried out.
During the glass transition, the viscosity of the system increases dramatically. This lead to the empirical definition of $T_g$ as the temperature at which the viscosity of the system reaches the value of $10^{13}$ poise.
While the mechanical properties of a glass are those of a solid, its microscopic structure is very similar to that of a liquid, with short-ranged correlations but lacking the long-ranged correlations typical of crystals.
Prerequisites:
- Thermodynamics
- Statistical Mechanics
Books and reviews on glasses and the glass transition:
Binder-Kob: Glassy Materials and Disordered Solids
Hansen-McDonald: Theory of Simple Liquids, Third Edition, Chap. 8
Theoretical perspective on the glass transition and amorphous materials
