Growth rate of crystal face

Curie s concept [7], which considered that the normal growth rates of crystal faces are proportional to the surface free energies and... 

It should be noted that there may be other possible factors affecting the normal growth rate of crystal faces. 

Figure 10.4. Growth rates of crystal faces in synthetic quartz [l]-[3] = normal growth rate of crystal faces = growth rate in weight A = reference data.

The linear growth rates of crystal faces vary enormously. Some approximate examples of the average rate for crystallization from solution are... 

In order to understand and make use of the phenomena of different growth rates of crystal faces in the presence of additives, computational methods can be employed. Established routine methods are employed to calculate the morphology... 

Both supersaturation and temperature can have different effects on the growth rates of different faces of the same crystal. Such occurrences have implications with respect to crystal habit, and these are dealt with in a later section. 

Because crystal growth is a surface phenomena, it is not surprising that impurities that concentrate at crystal faces will affect the growth rate of those faces and hence the crystal shape. With some surface active impurities, small traces, about 0.01%, are all lhat is required to change crystal habit during crystallization. These impurities can ... 

TABLE 16.3. Mean Overall Growth Rates of Crystals (m/sec) at Each Face ... 

Linear growth rate of a face which is the rate of displacement of a crystal face in a direction perpendicular to the face. 

The linear growth rate of a face can be expressed in terms of the step velocity, step height, and step spacing. Techniques used for in situ measurement of crystal growth rates as a function of supersaturation include the following ... 

If we examine these three models, each one makes some prediction about how crystals grow as function of supersaturation, temperature, or face area. In the case of the mononuclear model, Eq. (2.37) tells us that the crystal growth rate of a face is directly proportional to the area of that face. This would indicate that large faces grow faster than small faces, which contradicts the observation that the fastest growing faces on a crystal have the smallest areas while the slowest growing faces have the largest areas. This essentially eliminates the mononuclear model from serious consideration as a useful model. 

Figure 3.20 EfTect of L-glutamic acid on the growth rate of 101 faces of L-asparagine monohydrate crystals. (Reproduced with permission from Black et al. 1986.)...

It was indicated that L Phen adsorb preferentially on the (110) face and the growth rate of that face was not only suppressed but also it fluctuated with time as described previously. Such fluctuation suggests that the adsorption of L-Phen on the crystal surface is inhomogeneous. We observed previously a similar decrease of the growth rate for ammonium sulfate in the presence of chromium (III) ion(75). However, in that case the growth rate progressively decreased with time and did not fluctuate. Such difference may de related to the difference of the growth mechanism and characteristics of the surface of each material. 

The shape of a regularly brrilt crystal is not entirely defined by the lattice but also by the growth rates of its faces. The different types of crystal shapes are called prismatic, acicular, dendritic, straticular, or - in the case of uniform growth in all directions - isometric. 

Another important effect associated with the presence of impurities is that they may change the crystal habit. Habit alteration is considered to result from unequal changes in the growth rates of diflerem crystal faces. Davey reviews the role of impurities in the general context of habit modification. Surfactants, especially, have been observed to modify growth rates of individual faces and thereby change the habit of a crystal. ... 

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