Orientational Order in Biaxial Liquid Crystals

Abstract

$^{14}\mathrm{N}$ nuclear-quadrupole-resonance data show that the electric-field-gradient tensor at the $^{14}\mathrm{N}$ sites in terephthal-bis-butylaniline deviates from cylindrical symmetry in the biaxial smectic-$C$, smectic-$H$, and smectic-VI phases whereas it is cylindrically symmetrical in the uniaxial smectic-$A$ phase. The results suggest that in the smectic-$C$ phase the molecular tilt induces the rotational bias and not vice versa, whereas in the smectic-$H$ phase the situation is different and the results may be interpreted within the Meyer-McMillan model.