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Chapter II Solution Growth….
By applying the Periodic Bond Chain (PBC) theory developed by
Hartman and Perdock, one can find that the growth rate of a face is lower
when the fewer chains of strong bonds cross this face.
The growth of flat faces requires either a potential barrier for the
formation of two-dimensional nuclei be overcome or dislocation or other
defects for step generation be present. Both of the indicated generation
processes are slower, the higher the specific linear energy of the step is. This
energy is higher, the stronger are the PBC and crossing and give rises of
various oriented steps on a given face, i.e., parallel to the face. Moreover,
during growth, due to the arrival of particles from the adsorption layer to the
steps, the growth rate is higher and also the greater is the density of this
layer. The layer density reduces exponentially with increasing energy of the
bond between the adsorbed building-block particle and the surface, i.e., it
must again be least for the faces crossed by the least number of the most
energetic PBCs.
This correlation of surface energy and the growth rate results from the
crystal structure, which determines both quantities for any orientation. In short
the angular dependence of the growth rate is minimum for the same faces as
does the angular dependence of the surface energy.
In accordance to the postulates of PBC theory, the “specific weight” of
a face in the habit decreases in order F,S,K, ( Flat, Stepped, Kinked) faces.
The growth forms of KDP shows tetragonal (100) prisms and on both
ends tetragonal (101) pyramids. This is in agreement with the morphological
theory of Hartman and Perdock which predicts for ADP and KDP as F faces
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