Editing Nematic phase

[[Image:nematic_ellipsoid.png|Nematic phase for the hard 6x1x1 ellipsoid model. |thumb|right]]
The '''nematic phase''' of a [[liquid crystals |liquid crystal]] has orientational order, but no positional order
<ref>[http://www.oup.com/us/catalog/general/subject/Physics/MaterialsScience/?view=usa&ci=9780198517856 Pierre-Gilles De Gennes and J. Prost "Physics of Liquid Crystals"  (1995)]</ref>.
==Dielectric tensor==
In the uniaxial nematic phase, defining the ''z''-axis to be parallel to the nematic axis, one has

:<math>\epsilon_{\alpha \beta}= \begin{pmatrix}
  \epsilon_\bot & 0               & 0 \\
  0             &  \epsilon_\bot  & 0 \\
  0             &  0              & \epsilon_\|
\end{pmatrix}</math>

The anisotropy is defined as 

:<math>\Delta \epsilon = \epsilon_\| - \epsilon_\bot </math>. 

The response of a nematic liquid crystal
to an external electric field depends on both the sign and the magnitude of <math>\Delta \epsilon</math>.
==Discotic nematic phase==
[[Image:discotic_nematic_ellipsoid.png|Discotic-nematic phase for the hard 6x6x1 ellipsoid model. |thumb|right]]
==Biaxial nematic phase==
*[http://dx.doi.org/10.1103/PhysRevLett.97.267801  Jorge Peláez and Mark R. Wilson "Atomistic Simulations of a Thermotropic Biaxial Liquid Crystal", Physical Review Letters '''97''' 267801 (2006)]
*[http://dx.doi.org/10.1016/j.fluid.2007.03.026   Carl McBride and Enrique Lomba "Hard biaxial ellipsoids revisited: Numerical results", Fluid Phase Equilibria  '''255''' pp. 37-45 (2007)]
*[http://dx.doi.org/10.1063/1.2815804 Roberto Berardi, Luca Muccioli, and Claudio Zannoni "Field response and switching times in biaxial nematics", Journal of Chemical Physics '''128''' 024905 (2008)]
*[http://dx.doi.org/10.1088/0953-8984/20/46/463101   Roberto Berardi, Luca Muccioli, Silvia Orlandi, Matteo Ricci and Claudio Zannoni "Computer simulations of biaxial nematics", Journal of Physics: Condensed Matter '''20''' 463101 (2008)]
*[http://dx.doi.org/10.1063/1.3117925 Prabir K. Mukherjee and Kallol Sen "On a new topology in the phase diagram of biaxial nematic liquid crystals", Journal of Chemical Physics '''130''' 141101 (2009)]
*[http://przyrbwn.icm.edu.pl/APP/ABSTR/120/a120-3-1.html A. Kapanowski "Statistical Theory of Biaxial Nematic and Cholesteric Phases", Acta Physica Polonica A '''120''' pp. 351-367 (2011)]
*[http://dx.doi.org/10.1063/1.3646310 Roberto Berardi, Juho S. Lintuvuori, Mark R. Wilson, and Claudio Zannoni "Phase diagram of the uniaxial and biaxial soft–core Gay–Berne model", Journal of Chemical Physics '''135''' 134119 (2011)]
*[http://dx.doi.org/10.1063/1.4771592  Akihiko Matsuyama "Novel biaxial nematic phases of side-chain liquid crystalline polymers", Journal of Chemical Physics '''137''' 224906 (2012)]

==References==
<references/>
[[category: liquid crystals]]