磁场对双轴分子液晶的影响

Effect of Magnetic Field on Liquid Crystals Composed of Biaxal Molecules

在分子场近似下，研究分子双轴性对向列相液晶在各向同性相最低过冷温度的影响，以及对临界磁场的影响。当外加磁场大干临界磁场时，不发生向列相－各向同性相相变。理论结果表明，通过考虑分子双轴性，最低过冷温度Ｔ与相变温度Ｔｃ的比值向实验值靠近。随着分子双轴性的增加，临界磁场很快下降。

In the molecular field approximation, the effects of molecular biaxiality of nematic liquid crystals on lowest supercooling temperature in isotropic phase and on the critical magnetic field are studied. When the external magnetic field is higher than the critical value, the nematic-isotropic phase transition disappears. Theoretical results show that by taking account of the molecular biaxiality, the ratio of the lowest supercooling temperature T to the phase transition temperature T., approaches the experimental value. As the degree of biaxiality is increased, the critical magnetic field drops rapidly.