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Phase equilibria, fluid structure, and diffusivity of a discotic liquid crystal
Octavio Cienega-Cacerez1, José Antonio Moreno-Razo, Enrique Díaz-Herrera
1Departamento de Física, Universidad Autónoma Metropolitana-Iztapalapa, Avenida San Rafael Atlixco No. 186, Colonia Vicentina, Delegación Iztapalapa México, D.F. 09340, México.
Soft Matter
|April 11, 2014
Summary
Molecular Dynamics simulations reveal distinct behaviors in discotic fluid phases. The study identifies unique diffusion patterns and structural characteristics in isotropic, nematic, and two columnar phases.
Area of Science:
- Physical Chemistry
- Materials Science
- Computational Physics
Background:
- Discotic liquid crystals exhibit complex phase behaviors.
- Understanding molecular dynamics is crucial for predicting material properties.
- Gay-Berne models provide a framework for simulating anisotropic fluids.
Purpose of the Study:
- To investigate the volumetric phase diagram of a Gay-Berne discotic fluid.
- To characterize the structural and dynamic properties of isotropic, nematic, and columnar phases.
- To elucidate the mechanisms of anomalous diffusion in columnar liquid crystals.
Main Methods:
- Molecular Dynamics (MD) simulations using the Gay-Berne potential.
- Analysis of volumetric phase diagrams.
- Characterization using radial distribution functions and slab-wise fluid dynamics.
- Investigation of diffusion coefficients (anisotropic and transversal).
Main Results:
- The phase diagram includes isotropic (IL), nematic (ND), hexagonal columnar (CD), and rectangular columnar (CO) phases.
- The CO phase exhibits near-crystalline longitudinal structure and grain-boundary defects, while the CD phase shows short-ranged transversal structure.
- Anisotropic diffusion is observed in columnar phases, with a crossover favoring longitudinal diffusion at longer timescales.
- Anomalous diffusion in columnar phases arises from rattling, hopping, and drifting motions of discogens.
Conclusions:
- The study provides a detailed molecular-level understanding of phase transitions and dynamics in discotic fluids.
- Distinct structural and dynamic properties differentiate the hexagonal and rectangular columnar phases.
- The identified diffusion mechanisms offer insights into the transport properties of these materials.
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