Dislocations in Smectic and Columnar Phases.

Because of their translational symmetries, 1D (smectic) and 2D (columnar) positionally ordered liquid crystals show dislocations of translation of various characteristics. Their elastic and plastic properties, which depend strongly on the Burgers vector, their relationship with disclinations, and so on, make them original with respect to their counterparts in 3D solid crystals. These dislocations are also worth studying in some detail because of their role in complex phases with thermodynamical defects, such as TGB phases (smectics with periodic twist sub-boundaries), which we have already alluded to, or Moiré phases (columnar phases with periodic twist sub-boundaries), whose existence has been recently predicted. [ABSTRACT FROM AUTHOR]