Surface transitions in free standing films of antiferroelectric liquid crystals within the discrete phenomenological model

Within the discrete phenomenological model of antiferroelectric liquid crys tals we study phase transitions in free standing films. Commonly observed r ise as well as recently reported lowering of the temperature of the transit ion from the SmA to the tilted phase, compared to the bulk transition tempe rature, can be explained in view of the excess surface order in the first c ase or missing inter-layer interactions at the surfaces ill the second case . We also expose the possibility of forming non-planar SmCalpha phase in a narrow temperature region near the bulk SmA <-> SmC transition temperature, although the particular compound exhibits only SmA and SmC (or SmC*, if ch iral) phases in the bulk sample.