横向偶极作用下的双轴液晶分子近晶A理论

Biaxial smectic-A liquid-crystal theory with a traverse dipole interaction

利用Straley双轴分子两体作用势的理论模型,加上横向偶极矩作用,把Mcmillan描述单轴液晶分子近晶A理论推广为双轴液晶分子近晶A理论,利用分叉分析理论研究其相变.发现,当存在横向偶极作用时,存在单轴向列相(NU)到极性单轴相的相变(NU+及SmAu+)和单轴向列相到非极性相(NB、SmAu及SmAB)的相变,没有单轴向列相到极性双轴相(NB+及SmAB+)的相变.具体出现的液晶相与双轴性参数、偶极强度参数及近晶相参数的值的相对大小有关.

Using the Straley pair potential with a traverse dipole interaction, we have extended the Mcmillan theory which describes the smectic A formed by uniaxial molecules to a theory which describes the smectie A formed by biaxial molecules. We have also studied the phase transition via bifurcation analysis. We have found that there are phase transitions of uniaxial nematic to polar uniaxial phase （Nu ^＋ and SmAu^＋） and uniaxial nematic to non-polar phase （NB, SmAu and Sm Aa） with a traverse dipole interaction, but no uniaxial nematic to polar biaxial phase （NB^＋ and SmAB^＋）. Moreover, the phase transitions depend on the parameters ofbiaxial, dipole interaction and the smectic.