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Wetting and capillary nematization of a hard-rod fluid: a simulation study
M Dijkstra1, R van Roij, R Evans
1Debye Institute, Soft Condensed Matter Physics, Utrecht University, Princetonplein 5, 3584 CC Utrecht, The Netherlands.
Summary
We simulated hard spherocylinder fluids near walls, finding transitions to nematic surface phases and capillary nematization. These transitions are density and wall-separation dependent, suggesting a capillary critical point.
Area of Science:
- Physics
- Materials Science
- Computational Chemistry
Background:
- Understanding phase behavior of anisotropic fluids is crucial for materials design.
- Hard spherocylinders are a fundamental model for liquid crystals and self-assembling systems.
- Confined geometries significantly alter bulk fluid properties.
Purpose of the Study:
- To investigate the interfacial and confinement effects on hard spherocylinder fluid phase behavior.
- To explore transitions from uniaxial to biaxial surface phases and nematic film formation.
- To characterize capillary nematization in confined systems and identify critical phenomena.
Main Methods:
- Development and application of a Monte Carlo method for fluids at a single wall.
- Gibbs ensemble Monte Carlo simulations for phase equilibria in confined geometries.
- Simulation of hard spherocylinders with a length-to-diameter ratio of 15.
Main Results:
- Observed a transition from uniaxial to biaxial surface phases near a planar wall.
- Identified nematic film formation at the wall-isotropic fluid interface, with thickness dependent on density.
- Found a first-order capillary nematization transition in two-wall confinement, disappearing below a critical wall separation.
Conclusions:
- The study reveals complex surface and confinement-induced phase transitions in anisotropic fluids.
- Simulation results are consistent with theoretical models, validating the approach.
- A capillary critical point is proposed for the capillary nematization transition in hard spherocylinder fluids.
