Quick question about liquid crystals

  • Context: Graduate 
  • Thread starter Thread starter skrat
  • Start date Start date
  • Tags Tags
    Crystals Liquid
Click For Summary

Discussion Overview

The discussion centers on the order parameter S of liquid crystals as a function of temperature T, exploring theoretical expressions and their availability in literature. Participants express interest in obtaining a specific formula for S(T) to facilitate plotting and analysis.

Discussion Character

  • Exploratory, Technical explanation, Debate/contested

Main Points Raised

  • One participant notes a lack of exact expressions for the order parameter S as a function of temperature in the literature, questioning why this is the case.
  • Another participant clarifies that the expression for S(T) depends on the theoretical model and the specific system, indicating that there is no universal formula applicable to all liquid crystals.
  • This second participant suggests that experimental plots for different materials are more commonly available than theoretical formulas.
  • A third participant introduces the Maier-Saupe approximation as a potential avenue for discussion regarding the order parameter.
  • The fourth participant questions the relevance or implications of the Maier-Saupe approximation without further elaboration.

Areas of Agreement / Disagreement

Participants generally agree that there is no single exact expression for S(T) applicable to all liquid crystals, but the discussion remains unresolved regarding the specifics of the Maier-Saupe approximation and its relevance.

Contextual Notes

The discussion highlights the dependence of the order parameter on theoretical models and specific material properties, as well as the potential for experimental data to inform theoretical understanding.

skrat
Messages
740
Reaction score
8
After some reading, I noticed that everybody likes to mention the order parameter and most of the literature simply adds a graph, for example: http://www.personal.kent.edu/~bisenyuk/liquidcrystals/maintypes2.html

However, many (all of them, to be exact) seem to avoid the exact expression of order parameter S as function of temperature T. This makes me wonder why?
I would like to know the exact ##S(T)##, so I can plot it in mathemathica and play with it. Where could I find this? :/
 
Physics news on Phys.org
So you mean a theoretical formula for the order parameter versus temperature, right?
This will depend on the theoretical model and the specific system. And of course, on how this S is defined for the specific system.
There is no "exact" S(T) that applies to all liquid crystals.
It's more likely to find experimental plots for different materials.

Here you can find results obtained by using Landau's theory of phase transitions applied to liquid crystals (also called Landau-de Gennes in this case).
http://www.shu.ac.uk/research/meri/sites/shu.ac.uk/files/mmg-chapter_2.pdf

But the formula will depend on some parameters which have to be found experimentally.
 
What about Maier-Saupe approximation?
 
What about it?
 

Similar threads

  • · Replies 1 ·
Replies
1
Views
2K
  • · Replies 0 ·
Replies
0
Views
2K
  • · Replies 3 ·
Replies
3
Views
3K
Replies
0
Views
2K
  • · Replies 2 ·
Replies
2
Views
2K
Replies
2
Views
3K
  • · Replies 4 ·
Replies
4
Views
3K
  • · Replies 13 ·
Replies
13
Views
2K
  • · Replies 3 ·
Replies
3
Views
2K
  • · Replies 0 ·
Replies
0
Views
3K