Crystallization from solution nuclei formation rate

Figure 2.32 Formation of two-dimensional critical nucleus on a crystal surface. (From M. Ohara and R.C. Reid, Modeling Crystal Growth Rates from Solution, 1973, p. 20. Reprinted by permission of Prentice-Hall, Englewood Cliffs, New Jersey.)...

Models used to describe the growth of crystals by layers call for a two-step process (/) formation of a two-dimensional nucleus on the surface and (2) spreading of the solute from the two-dimensional nucleus across the surface. The relative rates at which these two steps occur give rise to the mononuclear two-dimensional nucleation theory and the polynuclear two-dimensional nucleation theory. In the mononuclear two-dimensional nucleation theory, the surface nucleation step occurs at a finite rate, whereas the spreading across the surface is assumed to occur at an infinite rate. The reverse is tme for the polynuclear two-dimensional nucleation theory. Erom the mononuclear two-dimensional nucleation theory, growth is related to supersaturation by the equation. 

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