Elastic properties of cholesteric liquid crystals

Depending on its chemical stmcture, the pitch of a cholesteric liquid crystal could take any value in the region from a few tenths of a micron to infinitely long. The periodicity of a cholesteric liquid crystal with the pitch Pg is PJ2, because n and - n are equivalent. Cholesteric liquid crystals are also called chiral nematic liquid crystals and denoted as N. Nematic liquid crystals can be considered as a special case of cholesteric liquid crystals with an infinitely long pitch. 

In practice, a cholesteric liquid crystal is usually obtained by mixing a nematic host and a chiral dopant. The pitch of the mixtore is given by 

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