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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.

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

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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 that defines the boundary between a solid and a…
Roman
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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 parameter and $\mathbf{n}$ the director, $i=x, y,…
user65112
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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 the third dimension". However, for a two…
user21090
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Difference between various theories of liquid crystals

Can somebody explain as to what is the difference between various theories of liquid crystals? Maier-Saupe Theory Onsager Theory Landau theory What's the advantages and disadvantages or limitations of each approach?
nitin
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What's the difference between Equivalence and Degeneracy?

I'm in a middle of an advanced stat-mech course, and we are now learning about liquid crystals (LC). In the last tutorial, we developed the Landau Free Energy of the LC system near the transition between the isotropic liquid and the nematic…
Yoav Zack
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Why do LCD pixels at the very edges of the screen "disappear" when looking at a shallow angle?

I've noticed something curious about my LCD screens (one of them is a TUF VG32VQ1B and the other an AOC I2269VW, if it makes a difference): If I look at them at a shallow angle, any bright line of pixels at the very edge of the screen fades out…
Kroltan
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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(like Schmitt trigger) which exhibit hysteresis and…
dexterdev
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What is Landau-de Gennes 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 crystals. I am particularly interested in Landau…
goat1123
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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 rods is based on this and I cant seem to find a…
nitin
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Does the Night Mode of the screen display (LCD) save more energy?

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 a common monitor display devise nowadays, so let…
wonderich
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Fourier Transform for sinusoidal number-density to obtain the structure function

I was reading chapter 2 of Chaikin and Lubensky, where I got stuck at this derivation of structure function. While talking about Smectics-A liquid crystal, it was mentioned that the molecules are aligned perpendicular to the layer. The introduction…
Soham Parmar
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Persistence length by De Gennes: how to make sense of the definitional equation?

I want to understand how De Gennes comes up with the concept of persistence length in microemulsions, and in particular a convenient equation that relates this persistence length to the thickness of the film through an exponential term depending on…
Glxblt76
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Order parameter

Order parameter: Suppose, for simplicity, that the molecules composing a nematic or cholesteric liquid crystal are rigid and rodlike in shape. Then we can introduce a unit vector v") along the axis of the ith molecule which describes its…
Rasha rashed
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Deforming a nematic line defect to a uniform configuration

In Nakahara section 4.9, "Defects in nematic liquid crystals", it is discussed that the order parameter for a nematic should be the real projective plane $\mathbb{R}P^2$, which has fundamental group $\pi_1(\mathbb{R}P^2) \cong \mathbb{Z}_2 =…
Kai
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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 please? I'll mostly be working in the lab, so it…
fazan
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