Luckhurst–Romano model of thermotropic biaxial nematic phase

Abstract

Recent experiments show that the long looked for thermotropic biaxial nematic phase is finally stabilized in a low mass liquid crystalline system. Inspired by this experimental observation we concentrate on some theoretical issues concerned with this phase. In particular we show that the simplest Lebwohl–Lasher biaxial model, as introduced by Luckhurst and Romano, is consistent with the minimal coupling Landau–de Gennes phenomenological approach. The model shows a rich spectrum of possibilities, in particular a direct isotropic–biaxial nematic phase transition. A possible bridge between molecular and phenomenological approaches, in particular an interpretation of the alignment tensor, is discussed.

Acknowledgements

This work was supported by the Polish projects (KBN) Nos. 5 P03B 052 20 and 2 P03B 086 23 and by the Fulbright Research Grant PPLS/04/06.

Notes

†. Note that to a given phase diagram its mirror image diagram with respect to the b = 0 line could be generated by a reversal of sign of the parameters in the Landau expansion that multiply terms with odd powers of Tr Q ³. Additionally N_U± should be replaced by in the mirror image diagrams.