Abstract
Deuterium NMR is a powerful technique to investigate the director distribution of a nernatic stab, because the NMR spectrum can contain a simple quadrupolar doublet whose separation us affected by the angle made by the director with the magnetic field vector. Using a contnnuum theory approach we calculated the director distribution in order to understand the experimental results. In this approach the torque balanced equations, involving the magnetic, electric and elastic energy, and a unified surface anchoring energy, was included. The equations with different boundary conditions were numerically solved to obtain the director distributions, which were employed to simulate the NMR spectra. The observed spectra for the strong anchoring condition showed a bistable director distribution below a critical value of the electric field. It was confirmed from the spectral simulations that two director distributions exist in a nematic slab with strong anchoring conditions. One is compatible with the weak anchoring condition, and the other vanishes at the critical point. At higher electrnc fields, for both strong and weak anchoring conditions, the director alignes parallel to the electric field.
