QUADRUPOLAR INTERACTION IN NEMATIC LIQUID-CRYSTALS

In this paper we show that the screened quadrupolar interaction among liquid crystal molecules cannot give rise to the nematic phase. This r esult follows from the fact that the associated splay and bend elastic constants appearing in the elastic energy density are negative. The e lastic energy density is evaluated by supposing that the interaction v olume has spherical shape, whose inner excluded part coincides with th e molecular volume. A generalization of our model to interaction volum e of ellipsoidal shape is also discussed. In both cases the total elas tic energy for splay-bend deformations is negative, indicating that th e molecules have no tendency to align along a common direction, as req uired by a nematic phase.