Effect of density variation on the Sm A-I phase transition properties

Based on a thermodynamic model, we investigate how the density variation influences the smectic (Sm A)-isotropic (I) phase transition. We find that the density variation shifts the smectic A-isotropic transition temperature, however, first-order nature of the transition remains the same. Here, we also examine the effect of high pressure on the thermodynamic quantities. The present analysis shows that the pressure strongly influences the enthalpy and density step at the clearing transition. The pressure dependence of the thermodynamic properties is incorporated through the pressure dependent second Landau coefficient and the coefficients which couple the nematic and smectic order parameters to the density. We find a close agreement between theoretical and experimental results. Furthermore, we discuss the implications of the results for achiral liquid crystals.