WHAT IS THE ORDER OF THE NEMATIC-SMECTIC TRANSITION?

It is usually assumed that the nematic to smectic transition in the Onsager limit is continuous. However, there is no hard (theoretical) evidence to support this conjecture. On the contrary, although Poniewierski performed his theoretical analysis assuming a continuous N-S transition, he pointed out that a (weak) coupling between orientation and translational degrees of freedom would make the transition first order [112].
We tried to determine the order of the nematic to smectic transition numerically. The results appear to depend on the type of periodic boundaries used in the simulations. In the case of normal periodic boundaries, we found evidence for a first-order N-S transition, whereas by applying shifted periodic boundary conditions as described in section 5.3.2.3 the transition becomes continuous.

• Normal periodic boundaries
• Shifted periodic boundaries