Industrial controllers growth type crystallizers

These apparent restrictions in size and length of simulation time of the fully quantum-mechanical methods or molecular-dynamics methods with continuous degrees of freedom in real space are the basic reason why the direct simulation of lattice models of the Ising type or of solid-on-solid type is still the most popular technique to simulate crystal growth processes. Consequently, a substantial part of this article will deal with scientific problems on those time and length scales which are simultaneously accessible by the experimental STM methods on one hand and by Monte Carlo lattice simulations on the other hand. Even these methods, however, are too microscopic to incorporate the boundary conditions from the laboratory set-up into the models in a reahstic way. Therefore one uses phenomenological models of the phase-field or sharp-interface type, and finally even finite-element methods, to treat the diffusion transport and hydrodynamic convections which control a reahstic crystal growth process from the melt on an industrial scale. 

CONTACT NUCLEATION. It has been known for a long time that secondary nucleation is influenced by the intensity of agitation, but it was not until the 1970s that the phenomenon of contact nucleation was isolated and studied experimentally. It is the most common type of nucleation in industrial crystallizers, for it occurs at low supersaturations where the growth rate of the crystals is at an optimum for good quality. It is proportional to the first power of the supersaturation, instead of the twentieth or more power for primary nucleation, so that control is comparatively easy without unstable operation. 

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