CONTRIBUTION OF THE SMECTIC-NEMATIC INTERFACE TO THE SURFACE-ENERGY

The contribution of the smectic-nematic interface to the surface energ y of a nematic liquid crystal sample is analyzed. By means of a simple model it is shown that the surface energy depends on the thickness of the region over which the transition smectic-nematic takes place. For perfectly flat substrates this thickness is of the order of the corre lation length entering in the transition. An estimate of this contribu tion shows that it is greater than the one arising from the nematic-su bstrate interaction. Moreover, it is also shown that the surface energ y determined in this way presents a nonmonotonic behavior with the tem perature.