Columnar phases and field induced biaxiality of a Gay-Berne discotic liquid crystal

We have studied a system of discotic particles with a central transverse di pole using Monte Carlo (MC) computer simulations at constant pressure. We h ave investigated several temperatures corresponding to nematic and columnar liquid crystal phases and determined the molecular and dipolar organizatio ns. Low temperature columnar phases are characterized by local biaxial orde ring of dipoles, even if the system is on the whole uniaxial. However, simu lations in the presence of a transverse field for different field and dipol e strengths show that the system has a large susceptibility and easily beco mes biaxial, making it potentially interesting for switching applications. An explicit formulation for the susceptibility in terms of biaxial invarian ts is derived.