液晶近晶C相双轴特性的统计理论

STATISTICAL THEORY OF BIAXIALITY IN Sc LIQUID CRYSTALS

采用格胞模型,定义了分子取向序参量、双轴序参量、质心位置序参量以及取向与质心位置耦合序参量.由自由能极小求得指向矢倾斜角与双轴序参量间的关系.对典型Sc相液晶物质TBBA,TBSA和NOBA的双轴序参量随温度的变化以及取向序参量和倾斜角对双轴序参量的影响作了数值计算,并与实验结果进行比较.表明这种双轴特性主要产生于Sc相的指向矢倾斜结构和分子取向的有序性.

With cell model, the orientational order parameter, the biaxial order parameter, the positional order parameter and the orientation and position coupling order parameter are defined, the functional dependence of the tilt angle on the biaxial order parameter and other order parameters is obtained by minimization of the free energy function. We have calculated the temperature dependence of the biaxial order parameter for TBBA, TB8A and NOBA, and compared with experimental results. It is shown that the biaxiality is due to the tilt structure and the orientational order of the Sc liquid crystals.