Surface integration controlled growth

Desolvation of the growth unit may occur anywhere in steps 2-A or the solvent may be adsorbed with the growth unit. As any of the above steps can be the rate limiting step in the crystal growth process and they are dependent on conditions such as supersaturation, temperature, additives or solvent, and the hydrodynamics of the system, crystal growth is generally divided into two main mechanisms volume-diffusion controlled or surface-integration controlled (Fig. 9). ... 

Crystal growth is volume-diffusion controlled when the diffusion of molecules from the bulk to the crystal surface is the rate-limiting step while growth is considered surface-integration controlled if the incorporation of a growth unit into the lattice is the slowest process. Many crystallization studies involving proteins. 

The kinetics of crystallization of such systems is often controlled by secondary attrition-induced nucleation and growth rates which are valid in the transition range between diffusion-limited and surface integration-limited growth. Diffusion hm-ited means G Ac//7j.. ... 

Garside (1971) defined an effectiveness factor for crystal growth that is a measure of the relative importance of diffusion and surface integration as the rate-controlling factors. The effectiveness factor is defined by the relation... 

Surface integration is the process by which the growth units of the crystallizing material are incorporated into the crystal lattice after they have been transported to the crystal surface. Two main mechanisms controlling surface integration are described here. 

Transport of the released solvent molecules to the bulk solution. ThesestepsareveryslmilartothosedescribedSec.2.3. Steps 1 andSare controlled by the usual diffusion kinetics, while steps 2, 3 and 4 are controlled by the kinetics of surface adsorption, surface diffusion and of integration of growth units at kinks. 

---