Nematic fluid structure in wall-field geometry

We describe an integral equation method for obtaining the distribution of a nematic fluid near a wall and interacting with a uniform orienting field. Complete density-orientational profiles are calculated for a model nematic with different wall-particle interactions and different orientations of the wall with respect to the field. For orienting walls we identify particular long-range correlations that are responsible for reorientation of the bulk nematic at zero external field. These correlations become stronger as the wall-particle interaction is increased in range; they become longer ranged as the orienting field is weakened. Special attention is focused on systems where the wall-particle interaction favors orientations perpendicular to the surface. The local director orientation can vary discontinuously with the distance from the surface when the orienting influences of the field and the wall are antagonistic. At high densities smectic-like structures appear. Adsorption phenomena are also discussed. For inert hard walls, the ordered fluid avoids the surface, and a surface layer where the particles tend to orient perpendicular to the bulk director appears. Experimentally, this might be seen as wetting of the wall by a less-ordered fluid. (C) 2005 American Institute of Physics.