Crystallization kinetics spreading rate

Surface Spiral Step Control. Many crystals grow faster at small supersaturation than allowed by Equation 7. This lead Frank (17) to suggest that steps may also originate from the presence of a screw dislocation, and that this kind of steps is not destroyed by spreading to the crystal edge, but continues infinitely. The rate law according to this theory is parabolic (7). We shall use the following version of the kinetic equation (10)... 

The kinetics of reversible decompositions are often highly sensitive to reaction conditions [43]. For example, the values of and E, for the decomposition of CaCOj show unusually wide variations, owing to the sensitivity of reaction rate to the availability of COj [44,45]. The spread of apparent E values is considerable [46] and some values are close to the dissociation enthalpy [1]. However, Beruto and Searcy [47] concluded that, under high vacuum conditions, the constant rate of interface advance in large crystals was probably controlled by the dissociation step in the absence of a perceptible contribution from the reverse process. The decomposition activation energy (205 kJ mol ) was appreciably larger than the dissociation enthalpy (178 kJ mol ). This is probably the most precise kinetic measurement for the calcite decomposition [48]. 

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