Monte Carlo simulation of smectic liquid crystals and the electroclinic effect: The role of molecular shape

Using Monte Carlo simulation methods, we explore the role of molecular shape in the phase behavior of liquid crystals and the electroclinic effect. We study a ``bent-rod'' mesogen shaped like the letter Z, composed of seven soft spheres bonded rigidly together with no intramolecular degrees of freedom. For strongly angled molecules, we find that steric repulsion alone provides the driving force for a smectic-C phase, even without intermolecular dipole-dipole interactions. For weakly angled (nearly rodlike) molecules, we find a stable smectic-A (SmA) phase and a strong electroclinic effect with a saturation tilt angle of about 19°. In the SmA phase we find evidence of vortexlike point defects. We also observe a field-induced nematic-smectic phase transition.