  It is demonstrated by analyzing real examples that phase transitions in
layered crystals occur like all other solid-state phase transitions by
nucleation and crystal growth, but have a specific morphology. There the
nucleation is epitaxial, resulting in the rigorous orientation relationship
between the polymorphs, such that the direction of molecular layers are
preserved. The detailed molecular mechanism of these phase transitions and
formation of the laminar domain structures are described and related to the
nature of ferroelectrics.
