Enhanced stability of the tetratic phase due to clustering
| Autor: | Yuri Martínez-Ratón, Enrique Velasco |
|---|---|
| Rok vydání: | 2009 |
| Předmět: |
[PACS] Molecular and microscopic models and theories of liquid crystal structure
Statistical Mechanics (cond-mat.stat-mech) Matemáticas Monte Carlo method Mathematical analysis Degrees of freedom (physics and chemistry) Phase (waves) FOS: Physical sciences Second moment of area Geometry Condensed Matter - Soft Condensed Matter Stability (probability) Square (algebra) Liquid crystal [PACS] Theory and models of liquid structure Cluster (physics) Soft Condensed Matter (cond-mat.soft) Condensed Matter - Statistical Mechanics alignment anchoring anchoring transitions surface-induced layering surface-induced ordering wetting prewetting transitions and wetting transitions [[PACS] Surface phenomena] Mathematics |
| Zdroj: | e-Archivo. Repositorio Institucional de la Universidad Carlos III de Madrid instname Web of Science |
| ISSN: | 1550-2376 1539-3755 |
| DOI: | 10.1103/physreve.79.011711 |
| Popis: | We show that the relative stability of the nematic tetratic phase with respect to the usual uniaxial nematic phase can be greatly enhanced by clustering effects. Two--dimensional rectangles of aspect ratio $\kappa$ interacting via hard interactions are considered, and the stability of the two nematic phases (uniaxial and tetratic) is examined using an extended scaled--particle theory applied to a polydispersed fluid mixture of $n$ species. Here the $i$--th species is associated with clusters of $i$ rectangles, with clusters defined as stacks of rectangles containing approximately parallel rectangles, with frozen internal degrees of freedom. The theory assumes an exponential cluster size distribution (an assumption fully supported by Monte Carlo simulations and by a simple chemical--reaction model), with fixed value of the second moment. The corresponding area distribution presents a shoulder, and sometimes even a well-defined peak, at cluster sizes approximately corresponding to square shape (i.e. $i\simeq\kappa$), meaning that square clusters have a dominant contribution to the free energy of the hard--rectangle fluid. The theory predicts an enhanced region of stability of the tetratic phase with respect to the standard scaled--particle theory, much closer to simulation and to experimental results, demonstrating the importance of clustering in this fluid. Comment: 9 pages, 9 figures |
| Databáze: | OpenAIRE |
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