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 shap e 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 sof t spheres bonded rigidly together with no intramolecular degrees of freedom . For strongly angled molecules, we find that steric repulsion alone provid es the driving force for a smectic-C phase, even without intermolecular dip ole-dipole interactions. For weakly angled (nearly rodlike) molecules, we f ind a stable smectic-A (SmA) phase and a strong electroclinic effect with a saturation tilt angle of about 19 degrees. In the SmA phase we find eviden ce of vortexlike point defects. We also observe a field-induced nematic-sme ctic phase transition. [S1063-651X(99)02111-X].