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Columnar phases of three-fold molecular structures.
Jean-Guy Demers1, Alain Caillé
1Département de Physique, Université de Montréal, Case Postale 6128, Succursale Centre-ville, Montréal, Quebec, Canada H3C 3J7.
Summary
This study investigates molecular ordering in liquid crystals, identifying key parameters for helical and positional order in columnar phases. Findings explain observed supercells and reveal new phases with helical order but no positional order.
Area of Science:
- Condensed Matter Physics
- Materials Science
- Crystallography
Background:
- Columnar liquid crystals exhibit complex ordering phenomena.
- Three-fold symmetric flat molecules present unique structural challenges.
- Understanding molecular order is crucial for material properties.
Purpose of the Study:
- To investigate the interplay of positional and helical orders in a specific liquid crystal phase.
- To identify the order parameters governing the observed supercell structures.
- To explore emergent phases arising from molecular ordering.
Main Methods:
- Utilizing Landau's group-theoretical framework.
- Defining and analyzing a set of three order parameters.
- Theoretical modeling of molecular arrangements and phase transitions.
Main Results:
- Identified order parameters explain supercells with intercalated columns and helical order.
- Confirmed experimental observations of opposite helicities.
- Characterized the first-order nature of the phase transition.
- Discovered a novel phase with helical order but lacking positional order along columns.
Conclusions:
- The Landau framework successfully describes complex ordering in columnar liquid crystals.
- The identified order parameters are key to understanding the observed supercell structures.
- New phases with unique ordering characteristics can emerge from molecular degrees of freedom.