Abrupt orientational changes for liquid crystals adsorbed on a graphite surface

We have determined the alignment of a Gay-Berne model liquid crystal near a graphite surface using Monte Carlo computer simulations. We find in this regime, where adsorption is dominating with respect to the intermolecular interactions, a discontinuous change in anchoring from planar to normal on going from the first to the second adsorbed layer. We also find that the structure of the first two adsorbed layers is not affected by different director orientations induced in the bulk liquid crystal, but is entirely determined by the surface potential. This is a clear example of a breakdown of standard continuum theory in the proximity of a surface.