Macroscopic and molecular symmetries of unconventional nematic phases
- 4 October 2006
- journal article
- research article
- Published by American Physical Society (APS) in Physical Review E
- Vol. 74 (4), 041701
- https://doi.org/10.1103/physreve.74.041701
Abstract
The effects of the molecular symmetry on macroscopic properties of conventional and unconventional nematic phases are investigated theoretically. These effects concern: (1) the form of the molecular orientation fluctuations, (2) the thermodynamic behavior and the list of stable ordered phases, (3) the effective symmetry of the molecules in the ordered phases. The order-parameter consists of tensors forming the main harmonics of the fluctuation distribution. In conventional models (valid for uniaxial molecules) a single tensor is sufficient while unconventional models (valid for less symmetric molecules) need several tensors with the same rank. We analyze the qualitative differences arising when the number of equivalent tensors varies. We show how to work out complete models in the general case, and to calculate the sequences of stable phases and the corresponding effective molecular symmetries. This yields, for each molecular group and each tensor rank, a complete classification and a deep insight into the structure of thermotropic nematics. This work generalizes the approach we have applied to polar nematics recently observed in polyester compounds and to unconventional uniaxial and biaxial phases of bent-core materials.Keywords
This publication has 25 references indexed in Scilit:
- Theory of uniaxial and biaxial nematic phases in bent-core systemsPhysical Review E, 2005
- Theory of chiral periodic mesophases formed from an achiral liquid of bent-core moleculesPhysical Review E, 2004
- Ferroelectricity in Liquid CrystalsMolecular Crystals and Liquid Crystals, 1999
- Ferroelectricity in the Lyotropic Cholesteric Phase of Poly L-GlutamateJapanese Journal of Applied Physics, 1998
- Unconventionals-Pairing Wave SuperconductivityPhysical Review Letters, 1996
- Ferroelectric Nematic Liquid Crystals: Realizability and Molecular ConstraintsPhysical Review Letters, 1988
- Between cylinders and bilayers : structures of intermediate mesophases of the SDS/water systemJournal de Physique, 1987
- Nematic-hexagonal discotic phase transition: Pretransitional enhancement of elastic constantsPhysical Review A, 1983
- NMR in Spinning Samples of Biaxial Liquid CrystalsPhysical Review Letters, 1979
- Biaxial order parameters in liquid crystals: Their meaning and determination with nuclear quadrupole resonancePhysical Review A, 1978