  Under an electric field, chiral smectic liquid crystals transit usually to
the unwound SmC* phase where the helical structure is completely unrolled.
Sometimes the sample transits initially towards an intermediate polar state
before the total destruction of the helix. Based on the extension of the H-T
model, a theoretical study of these field-induced phase transitions was carried
out. Two hypotheses of the dynamics that give rise to the appearance of the
intermediate phase have been discussed. The results of a numerical analysis
confirm the known experimental results; the intermediate phase has a
three-layer periodicity structure.
