Global Phase Diagram of Maier–Saupe Model and Inhomogeneity Due to Walls

Opto-Electronics Review

2009

Freedericksz transition, which is usually analyzed by an elastic theory, is studied on the basis of statistical mechanical ground, where nematics with positive dielectric anisotropy in homogeneous anchoring cell is exposed to an electric field in the direction of wall normal. In low temperature region, an oblique axial symmetry breaking occurs, which is nothing but the Freedericksz transition. In high temperature and high field region, biaxial nematic phase with principal axis parallel to the field direction at interior area of the system is proved to appear. A phase diagram on the field versus temperature plane is obtained and compared with the one at a bulk with common biaxial symmetry, where both of electric and magnetic fields are applied in directions perpendicular to each other. In the latter, no symmetry breaking occurs, in contrast with the former case above-mentioned, and the reason why this difference occurs is elucidated.

Section: Results Of Numerical Analysesmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Molecular theoretic study of Freedericksz transition. Symmetry breaking of oblique axial order

Kio

Opto-Electronics Review

2009

“…In fact, such an analysis is shown to be useful in order to uncover the mechanism of smectic A-C * phase transition, 9 and I-N phase transition of Maier-Saupe model. 13,14 For thin system version of the model we analysed in the present paper, we have investigated the phase transitions and thermal behaviour of physical quantities by utilising the phase diagram obtained in the present paper, which will be reported in a near future. 15 This study was partly supported by a Grant-in-Aid from the Ministry of Education, Culture, Sports, Science and Technology (No.…”

Section: Summary and Discussionmentioning

confidence: 99%

Isotropic, Nematic and Smectic A Phase Behaviour in a Fictitious Field

2004

J. Phys. Soc. Jpn.

Self Cite

Phase behaviours of liquid crystals under external fields, conjugate to the nematic order and smectic order, are studied within the framework of mean field approximation developed by McMillan. It is found that phase diagrams, of temperature vs interaction parameter of smectic A order, show several topologically different types caused by the external fields. The influences of the field conjugate to the smectic A phase, which is fictitious field, are precisely discussed.Comment: To be published in J. Phys. Soc. Jpn. vol.73 No.

“…In the system with negative electric (magnetic) anisotropy, the nematic order is biaxial, in which the rotational symmetry around the field direction is broken spontaneously. The prediction that an order of the phase transition changes from the first order to the second order at a tricritical point is particularly of interest [8,9]. On the other hand, it is noteworthy that the nematic order cou− ples with both electric field and magnetic field.…”

Section: Introductionmentioning

confidence: 99%

Effects of fields and anchoring on biaxial nematic ordering

Yasen

Opto-Electronics Review

2009

Symmetry of a nematic liquid crystal phase is broken by an anchoring wall and also by an external field. Nematic system sandwiched between biaxial anchoring walls is introduced as a correspondent to a bulk nematic system exposed to a couple of fields, an electric field and a magnetic one in directions perpendicular to each other, and thermal behaviours of the system are studied. The crossover between a homeotropic structure and homogeneous one occurs, similarly to the bulk system in the fields, in which the anchoring condition of coexistence is shown to have the same expression as the one at the bulk. As to a characteristic phenomenon at the sandwiched system, it is proved that an appearance of a biaxial nematic order suppresses a uniaxial nematic order. A surface transition, i.e., a wetting phenomenon is shown to occur also in the biaxial nematics, even though the uniaxial order is suppressed therein.