Calamitic and antinematic orientational order produced by the generalized Straley lattice model

Area of Science:

• Condensed Matter Physics
• Materials Science
• Statistical Mechanics

Background:

• Investigating molecular ordering in condensed phases is crucial for understanding material properties.
• Classical lattice models provide a framework for studying phase transitions and emergent behaviors.
• Antinematic and calamitic interactions influence the orientational order of molecules.

Purpose of the Study:

• To investigate the phase behavior of a D2h-symmetric particle model in a simple-cubic lattice.
• To analyze the influence of a tunable calamitic coupling on antinematic ordering.
• To determine the low-temperature phases and their transitions as a function of coupling parameters.

Main Methods:

• Utilized a classical lattice model with nearest-neighbor interactions.
• Employed Monte Carlo simulations and molecular-field theory for analysis.
• Investigated a potential model based on scalar products of molecular arm vectors.

Main Results:

• The model exhibits distinct low-temperature phases: uniaxial nematic, antinematic, and orientationally disordered.
• Phase transitions are observed as a function of the calamitic coupling constant (-z).
• For small -z, a sequence of uniaxial nematic, antinematic, and disordered phases appears; for large -z, only uniaxial calamitic behavior is found.

Conclusions:

• The interplay between antinematic and calamitic couplings dictates the emergent orientational order.
• The model successfully predicts transitions between different nematic phases.
• Macroscopic biaxiality is suppressed in the considered model configurations.