Crystallization in glass-forming liquids: Effects of decoupling of diffusion and viscosity on crystal growth

• The effect of decoupling on crystal growth processes is analyzed.
• A criterion is formulated allowing one to establish the decoupling temperature Td based exclusively on measurable data.
• A theoretical model is developed for the description of growth both above and below the decoupling temperature.
• A relation for Td is derived correlating its value with glass transition temperature and fragility.

The effect of decoupling of viscosity and diffusion, i.e. of the breakdown of the Stokes–Einstein–Eyring equation, on crystal growth processes is analyzed. A criterion is formulated which gives the possibility to establish, based exclusively on experimentally measurable data, whether and at which temperature decoupling occurs in a given system. The results of our analysis are compared with alternative approaches. A theoretical model is advanced allowing one to describe the crystal growth kinetics in the whole temperature range where crystallization may proceed, i.e., between the absolute zero and the melting or liquidus temperature. A relation is derived allowing one to correlate the decoupling temperature with the glass transition temperature, and the fragility of the liquid. The results are confirmed by experimental data.