Molecular Models for Simple Smectic Phases

McMillan W L 1971 Simple molecular model for the smectic A phase of liquid crystals Phys.Rev A 4 1238-46... 

W. L. McMillan, Simple Molecular Model for the Smectic-A Phase of Liquid Crystals, Phys. Rev., A4, p. 1238(1971). 

In the isotropic phase, ry = r = cr = 0 in the nematic phase, ry 0, r = <7 = 0 in the smectic-A phase ry 0, r 0, a 0. For perfect order all three tend to unity. Part of the task of molecular theory is, of course, to calculate the temperature dependence of these order parameters. Again we point out that although the three quantities of Eq. [11] are sufficient to parametrize simple mean field models, a good approximation to the true distribution function, /(cos, 2) requires many terms in Eq. [7]. 

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