Phase transitions of smectic-isotropic phase in liquid crystals

Smectic phases formed by rod-like molecules with long axes that are parallel and also arranged in planes. The smectic-isotropic phase transition is a phase change from the liquid crystal to the liquid phase. In this work, we use a mobile 6-state Potts model to study the nature of the smectic-isotropic phase transition. Microscopic interactions between neighbouring molecules in this model are supplemented with the Lennard-Jones potential. This study applies Monte Carlo simulation with the Wang-Landau algorithm to determine the characteristics of smectic-isotropic phase transitions. It is shown clearly that the smectic phase goes to the isotropic phase and undergoes a first-order transition. The results also point out that when the temperature increases, molecules on the surface are orientationally disordered, then the molecules gradually lose their positional order. These results are in agreement with experiments that revealed the coexistence of the smectic and isotropic phasesduring the phase transition process in accordance with experimental studies.