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Phase behaviour of parallel hard rods in confinement: an Onsager theory study.
Alexandr Malijevský1, Szabolcs Varga
1Department of Chemical Engineering, Imperial College London, South Kensington Campus, London SW7 2BZ, UK.
Summary
Confinement inhibits nematic-smectic A phase transitions in hard cylinders. Instead, layering transitions emerge due to pore geometry, shifting towards bulk behavior as pore width increases.
Area of Science:
- Physics
- Materials Science
- Physical Chemistry
Background:
- Understanding phase transitions in confined systems is crucial for materials science.
- Onsager's second virial theory provides a framework for studying liquid crystal behavior.
Purpose of the Study:
- To investigate the impact of confinement on positional ordering in hard cylinders.
- To analyze the interplay between bulk and confined system theories.
Main Methods:
- Utilizing Onsager's second virial theory for parallel hard cylinders.
- Developing a formalism linking bulk and confined system theories via a w(ij) kernel function.
- Simulating systems within slit-like pores with hard walls.
Main Results:
- Hard walls inhibit the second-order nematic-smectic A phase transition.
- Infinite first-order layering transitions appear due to cylinder accommodation issues.
- Coexisting curves are bounded by lower critical points, with properties approaching bulk behavior as pore width increases.
- A single hard wall leads to a critical wetting transition inducing layering.
Conclusions:
- Confinement fundamentally alters phase transition behavior compared to bulk systems.
- Layering transitions are a key feature of hard cylinder systems in confined geometries.
- Pore width significantly influences the proximity of confined system properties to bulk behavior.
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