Theory of Phase Transitions of a Biaxial Nematogen in an External Field

Abstract

Landau-de Gennes (LdeG) theory and a microscopic model of interacting quadrupolar tensors, also known as the dispersion model, are used to analyze the effect of an external field on a nematogenic liquid crystal material having the zero field phase sequence biaxial nematic-uniaxial nematic-isotropic liquid as temperature increases. Although both approaches give qualitatively the same results the dispersion model does not reproduce all features of the phenomenological phase diagrams. For example, the biaxial-uniaxial transition for positive uniaxial anisotropic susceptibility is found to shift with field to either higher or lower temperature, depending on the values of the coefficients in the LdeG expansion, while the molecular model shows only the first type of behavior.

Keywords:

• Biaxial nematic
• Landau-de Gennes theory
• liquid crystal phase transitions
• molecular modeling

Acknowledgment

D.W.A. thanks Samsung Electronics Company Ltd. for partial support of this research. The work has also been supported by the International PhD Projects Programme of the Foundation for Polish Science within the European Regional Development Fund of the European Union, agreement no. MPD/2009/6.