Amorphous configurational state: energy landscape
Amorphous and glassy states of molecular and pharmaceutical compounds: general properties

The difference in nature between the states of a system, above and below T _g , can be represented schematically on a Gibbs free energy diagram (figure 17 ). Between T _g and T _m , the system is metastable, but in a state of equilibrium. The situation corresponds to the bottom of the free energy potential well corresponding to the supercooled liquid. Its level is, however, higher than that of the bottom of the well corresponding to the crystal. Below T _g , the system is not even metastable, but unstable. From a free-energy point of...