Effect of different sizes of subcritical nuclei on kinetics of transformation in the solid state

Amorphous modifications of the sulfur group elements contain embryos with different numbers of members of the stable nucleus. During the transformation these embryos form stable nuclei at different rates: the larger the number of members, the more rapid is the formation of a stable nucleus. The nucleation rate depends on the rate of increase of an individual embryo to the critical size and on the number of embryos. Four cases of the transformation are discussed depending on the number of embryos of different sizes. The value of the Avrami exponent for each case was given. Results of the discussion were used to explain the transformation kinetics of amorphous modifications of selenium and sulfur.