EXPERIMENTAL-DETERMINATION OF LANDAU-EXPANSION COEFFICIENTS IN FERROELECTRIC LIQUID-CRYSTALS

A technique of measuring basic Landau-expansion coefficients in ferroe lectric liquid crystals is proposed. The method is based on combined m easurements of the tilt angle and the total polarization of ferroelect ric liquid crystals at various temperatures and electric field strengt h in the vicinity of the ferroelectric S-C-paraelectric S-A* transiti on. The chiral and non-chiral coefficients of the free energy expansio n are obtained from these data by a numerical analysis based on the ge neralized Landau-model of ferroelectric liquid crystals. The method is applied to two commercial FLC mixtures and the results are reported.