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Questions tagged [liquid-crystal]

Liquid crystals (LCs) are matter in a state that has properties between those of conventional liquid and those of solid crystal.

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61 views

Thermal hysteresis and its physical significance in lipid membranes?

We usually associate the phenomenon of hysteresis with memory in the system. For example, magnetic hysteresis is the basis of hard disks(if I recall it correctly). There are also electronic circuits(...
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What is the representation of the different classes of nontrivial textures in an ordered field of biaxial nematics in terms of $SU(2)$-like rotations?

I was reading Mermin's classic review on Topological Defects in Ordered Media, in which he describes ordered media with non-Abelian Fundamental Groups by taking the example of biaxial nematics with ...
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38 views

Liquid crystals resource recommendation

I'm going to work with liquid crystals during my summer internship and I am so woefully unprepared. Could you please recommend me some book or some review articles that cover the essential concepts ...
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Bond order correlation function

I am trying to compute the bond order correlation function, $g_6$. It is defined based on the bond order parameter: $$\psi_6(x_i) = \frac{1}{N_i}\sum_{i=1}^{N_i}{\exp(i6\theta_i^j)}$$ where $\theta_i^...
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Are the curvature Frank elastic constants of the liquid crystal the no-zero elements of the 6x6 elastic (stiffness) matrix?

I was reading Landau's book on elasticity theory, and it raised this doubt. Can anyone help me?
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How can I deduce the magnetic susceptibility tensor of a biaxial liquid crystal in its nematic phase?

I know from de Gennes' book [1] that the (magnetic) susceptibility tensor $\chi_{\alpha\beta}$ of an uniaxial liquid crystal in its nematic phase can be written as \begin{align} \chi_{\alpha\beta}&...
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What it means to be that liquid crystals are thermodynamically stable?

When we heat some solids, they don't pass into liquid state directly. Rather they form a mesomorphic phase called liquid crystals.Now when we heat liquid crystal, they are converted into pure liquids. ...
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40 views

Defect in liquid crystals

What are +1 and -1 topological defects in liquid crystal ? What are 1/2 and -1/2 topological defects in liquid crystals ? I put a lot of time to search for it but I could not find an easy ...
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1answer
534 views

Generating X-ray diffraction patterns from atomic coordinates

I have a list of atomic coordinates for a periodic system as a result of a molecular dynamics simulation. I want to use those coordinates and predict what it's 1D diffraction pattern looks like. The ...
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53 views

What is Landau-deGenes Expansion?

I am an undergraduate student in an introduction to condensed matter physics course and I am struggling to understand the process of Landau expansion of order parameter S as it relates to liquid ...
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1answer
97 views

LCD's working principle [closed]

In the image's information it says ''Liquid crystal device windows are in the group of electrically activated smart windows in which normal "off" condition of the glazing is a translucent milky white. ...
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3answers
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Why we use liquid crystals in LCDs?

Does anyone know why do we use Liquid crystals in LCD's.Why can't we use transistors to switch light on/off instead of using polarizing filters to change pixels light/dark.Is there any specific reason ...
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What is the viscosity difference between a solid and a liquid

The pitch drop experiment, for example, shows bitumen as a liquid, even though it appears to be a solid, and then there is the "glass: solid or liquid" debate. Is there a numerical value in viscosity ...
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1answer
76 views

Deformation in the nematic phase of a liquid crystal survived in solid state

Does anyone know if I cool a liquid crystal with a deformed nematic phase quickly it will preserve the deformation in the crystal lattice? I didn't never see that in classical books on liquid crystals....
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1answer
134 views

Full time derivative of the Frank-Oseen energy. Mathematical problem

I am studying liquid crystal theory with the book Kleman, Lavrentovich, Soft Matter Physics. In the Ericksen-Leslie theory, Frank-Oseen energy density is: $$ f=0.5*(K_1*div^2 (n)+K_2 *(n*curl(n))^2+...
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1answer
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Why use class multiplication to describe topological entangling and merging?

I'm studying some references about topological defects in ordered media like Soft matter physics: An introduction by Kleman and the Review modern physics paper The topological theory of defects in ...
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1answer
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Equivalent tensor order parameters of nematic liquid crystals?

I found in the literatures two different definitions of the tensor order parameter of nematic liquid crystals. One is $$ Q_{ij}=\frac{S}{2}(3n_{i}n_{j}-\delta_{ij}), $$ where $S$ is the scalar order ...
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1answer
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How to calculate excluded volume in Onsager's hard-rod model?

Can somebody please provide a derivation of how to calculate excluded volume of two rods with angle of intersection being $\gamma$. rods are cylinders, capped with semi-spheres. Onsager theory of hard ...
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1answer
128 views

Is the $2\pi$ disclination topologically stable for a 2d nematic liquid crystal?

For a three dimensional liquid crystal, a $2\pi$ or charge $1$ disclination is topologically unstable. The is generally explained as the disclination can lose its core singularity by "escaping from ...
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216 views

Difference between various theories of liquid crystals

Can somebody explain as to what is the difference between various theories of liquid crystals? 1) Maier-Saupe Theory 2) Onsager Theory 3) Landau theory What's the advantages and disadvantages or ...
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1answer
166 views

Molecular field meaning in Liquid Crystal Theory

Given the Frank-De Gennes free energy $F = \int f(\boldsymbol{p},\nabla\boldsymbol{p}, ...)\ d\boldsymbol{x},$ for liquid crystals (see De Gennes-Prost, p. 107, formula 3.21), the vector $$h_{i}=-\...
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491 views

What is the difference between emission wavelength and lasing wavelength?

I'm reading an article on liquid crystal lasers and they're saying periodicity determines lasing wavelength and cavity geometry determines emission wavelength. What is the difference?
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Does the Night Mode of the screen display (LCD) save more energy? [closed]

In some cases, we can enable the Night Mode (reversing the bright and dark color of the display; such as White Text, Black Background) for the screen display. LCD(Liquid-crystal display) seems to be ...