Field-Induced Shifts of the Phase Transition Temperatures

1 Field-Induced Shifts of the Phase Transition Temperatures 

When an electric field is applied to a uniaxial liquid crystal a new term must be added to the expression for free energy of the medium 

In the case of second-order transitions we must compare a gain in the electric energy with a loss of the soft-mode elastic energy. For example, for the smectic A-smectic C phase transition the shift of the Tca point is [81] 

For the chiral smectic C phase instead of the quadratic term, AeE /Sn, the linear term proportional to the spontaneous polarization PsE) must be taken into consideration. 

FIGURE 1.21. Field-induced changes in order parameters for a smectic A liquid crystal. S is the orientational order parameter, R is an order parameter describing the coupling of the translational and orientational order. The field increases from curve 1 to curve 3. 

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