Phase transition starts via formation of small nanoparticles called nuclei. Formation of nuclei plays the crucial role as this process predetermines structure and the physical properties of the new forming material. Up to this time, we do not fully understand to this process. Molecular simulations (MS) enable to determine the structure of newly forming clusters. However, the timescale in MS is too short (about nanoseconds).
The beginning of the phase transition process is often detected via thermal analysis or light scattering techniques when critical supercooling (or supersaturation) is detected. However, it is not clear how many particles of various sizes formed at the critical supersaturation.
We numerically solved kinetic equations to determine the size distribution of nuclei as a function of time and size near critical supercooling, when the first particles are created [1]. We have determined the maximum size of nuclei rmax and also the growth rate v=drmax/dt. In sufficiently large volumes of the parent phase, the growth rate after reaching of certain minimum increases with time to the flat interface limit. However, in small volumes depletion of the parent plays an important role and the growth rate of particles after reaching some maximum decreases in time.
This work was supported by the Project no. LD1504 of the Ministry of Education, Youth and Sports of the Czech Republic (COST Action CM1402).
[1] Z. Kožíšek, P. Demo: J. Cryst. Growth 475 (2017) 247.
