Monte Carlo Simulation of Smectic Liquid Crystals and the Electroclinic Effect: the Role of the Molecular Shape

摘要

Using Monte Carlo simulation methods, we explore the role of molecular shapein the phase behavior of liquid crystals and the electroclinic effect. We studya "bent-rod" mesogen shaped like the letter Z, composed of seven soft spheresbonded rigidly together with no intra-molecular degrees of freedom. Forstrongly angled molecules, we find that steric repulsion alone provides thedriving force for a smectic-C phase, even without intermolecular dipole-dipoleinteractions. For weakly angled (nearly rod-like) molecules, we find a stablesmectic-A (SmA) phase and a strong electroclinic effect with a saturation tiltangle of about 19 degrees. In the SmA phase we find evidence of vortex-likepoint defects. We also observe a field-induced nematic-smectic phasetransition.