Gibbs free energies, amorphous solids

Figure 1. The estimate of excess Gibbs free energy (AG) against temperature suggesting a first-order transition. The solid lines (indicated as amorphous 1 and 2) represent two extreme estimates of AG for the amorphous phase and the dashed lines are extrapolation of these AG into the liquid phase. The dotted line shows AG for the liquid phase and the long-dashed is the reference crystal phase value. Tai, Tic, and Tac (dot-dashed line) represent liquid-amorphous, crystal-liquid, and oystal-amorphous phase transition temperatures, respectively. [Adapted from Donovan et al. [40] with permission.)...

What is phase competition in the process of a solid-state reaction. Consider a diffusion couple of two mutually soluble components A/B, which diffuse into each other forming intermediate phases and, possibly, a solid solution, beta binary system A-B have three stable intermediate phases 1, 2, 3, a metastable compound 4, and an amorphous phase 5. The dependence of the Gibbs free energy on the composition of these phases is given in Figure 4.1. 

Gibbs energy See free energy. glass An ionic solid with an amorphous structure resembling that of a liquid. 

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