CANADIAN JOURNAL OF PHYSICS, vol.96, no.7, pp.688-692, 2018 (SCI-Expanded)
Smectic A - Smectic C* transition in the ferroelectric liquid crystal (C7) is studied as a function of the electric field and the temperature. By expanding the free energy in terms of the tilt angle theta (Smectic C* phase) and the polarization P with a linear coupling between theta and P (P theta) in mean field theory, the tilt angle is calculated as a function of the electric field (theta versus E) at constant temperatures with respect to the transition temperature for C7 using the observed data from the literature. Also, by extracting the tilt angle from the observed electric displacements at various temperatures (at constant field strength) the inverse tilt angle susceptibility (chi(-1)(theta)), derived from the free energy, is fitted to the observed data for the dielectric constant and the fitted parameters are determined. Our calculated theta and chi(theta). show that the mean field theory explains adequately the observed behavior of the Smectic A - Smectic C* transition in the liquid crystals C7.