Crystallization models.

Three models of crystal growth - reproduced from Yu et. al.

The HNB model assumes that GC growth occurs via the coalescence of homogeneous crystal nuclei onto existing crystal surfaces at a rate defined by the β relaxation of the liquid, rather than the alpha relaxation.

The model of tension-induced interfacial mobility postulates that GC growth is the same as crystal growth in the diffusion-controlled mode, except that diffusion is enhanced at the crystal/liquid interface due to the tension created by the density difference between the crystal and the liquid. Because a crystal usually is denser than a liquid or a glass, crystal growth may induce extensional stress around a crystal due to volume contraction. While some argue that this stress should slow crystal growth (e.g., by thermodynamically destabilizing the crystal, Tanaka suggests that this stress “should provide the free volume to the particles surrounding the crystal, increase their mobility, and help further crystallization.” This process would be possible only at temperatures so low that flow cannot relieve the stress on the time scale of crystal growth.


The model of solid-state crystal growth by local mobility assumes that the molecular motions responsible for GC growth are not the alpha process (the motion responsible for diffusion controlled growth), but a local molecular motion native to the glassy (solid) state.