A phenomenological description is given of the mesophases which may arise below a liquid formed from achiral molecules possessing a transverse dipole, as the result of a coupling between their tilt and polar orders. Six stable mesophases are found. Two of them have a cholesteric biaxial structure. The others display antiferroelectric or ferrielectric, incommensurately modulated, structures with in-plane or out-of-plane spontaneous polarization. The in-plane polarized structures become unstable under application of a longitudinal electric field. Other field-induced effects are discussed.

• Received 29 November 1999

DOI:https://doi.org/10.1103/PhysRevE.62.5143