Longitudinal spontaneous polarization and longitudinal electroclinic effect in achiral smectic phases with bent-shaped molecules

The stable smectic configurations associated with achiral bent-shaped molec ules are investigated theoretically. Five different configurations of the m olecules within the layers are found, among which two possess a spontaneous longitudinal polarization, consistent with the (n) over cap --> -(n) over cap symmetry. Under application of a longitudinal electric field these conf igurations can give rise to remarkable held effects, such as a three-state switching of the transverse polarization under alternating field, and a lon gitudinal electroclinic effect. [S0031-9007(99)08447-1].