Crystal Habit and Facet Growth: Shape Changes Need a Face-Specific Mechanism

Define the Phase or Process Boundary

Ma and colleagues' primary IUCr study distinguishes growth along individual crystal-face directions from one size number. Facet-specific growth can change external shape. A size-equivalent sphere or one projected dimension does not retain all those directional changes.

Review a Hypothetical Comparison

In an invented geometry, two pairs of opposite faces initially span 40 µm in perpendicular directions. Assign symmetric face-normal growth of 0.5 µm/min in the first direction and 0.1 µm/min in the second for 30 min. Their full dimensions become 40+2×0.5×30=70 µm and 40+2×0.1×30=46 µm. The dimension ratio changes from 1 to about 1.522. Calling both directions a single growth rate would erase the mechanism behind the changing habit.

Keep the Evidence with the Decision

Keep face identity, direction and whether the measured distance spans one face or an opposite pair in the record. Establish which dimensions are actually observed and which are assumed. Compare changes over a stated time interval and solution state. Shape change alone does not identify a new polymorph; structural-form evidence belongs in a separate review.

The symmetric rates and geometry are assigned and are not the IUCr paper's measurements. This illustration proposes no imaging procedure, real growth law or shape target.

Does the proposed habit explanation identify relative growth of crystallographic faces?

This blank worksheet is for your own project. It contains no H M machine trial result.

Customer Questions

Primary References

These references support the technical principles discussed in this guide. The worked examples and review questions are educational.

• Ma and colleagues' primary IUCr study
• Reference from hmpharmamachines.com