Implications of Symmetry for Polar Molecular Crystals

Dear Colleagues,

Polar crystal structures (those belonging to one of the 10 pyroelectric point groups) represent special objects because of the existence of a polar axis and corresponding (hkl) faces carrying a charge. Here, a number of fundamental issues come up concerning, e.g., mechanisms for charge or dipole/electrical field compensation. What is the true stationary state of such an object? From quantum mechanics we know that a system in its stationary state cannot carry a permanent dipole moment. What are, thus, the possible domain states, particularly for non-ferroelectric polar structures? How can charges from the environment account for compensating surface charge? What do we know experimentally about this? Why do faces opposite in signs show different hkl faces and different growth speeds? What is the influence of the morphology on the inner and outer electrical field (compensated vs. non compensated state) and on the growth behavior?

Many other questions may come up from colleagues in crystallography, physics and chemistry, who would like to contribute to this Special Issue of Symmetry. Just for simplicity on the matter, we would like to restrict contributions to molecular crystals of neutral molecules. Both theoretical (analytical, computational) and experimental work (crystallography and crystal physics) are welcome for consideration.

Prof. Dr. Jürg Hulliger
Guest Editor

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• polar molecular crystals
• polar axis and faces
• domain states
• stationary state
• charge compensation
• computational work
• morphology