ABRUPT ORIENTATIONAL CHANGES FOR LIQUID-CRYSTALS ADSORBED ON A GRAPHITE SURFACE

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