Molecular model of biaxial ordering in nematic liquid crystals composed of flat molecules with four mesogenic groups.
Molecular model of biaxial ordering in nematic liquid crystals composed of flat molecules with four mesogenic groups.
复制标题
由具有四个介晶基团的扁平分子组成的向列液晶双轴有序的分子模型。
DOI：
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发表时间：
2010
期刊：
影响因子：
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通讯作者：
J. Vij
中科院分区：
文献类型：
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作者：
M. Gorkunov;M. Osipov;A. Kocot;J. Vij
本文分析了由四个刚性连接到同一中心的介晶基团组成的具有C2 h对称性的扁平分子的模型液晶中单轴和双轴液晶相的相对稳定性。提出了基于介晶基团间Gay-Berne相互作用的分子间对势的广义有效四极平均场势，并对其常数进行了数值计算。系统地分析了这些常数对分子形状参数的依赖关系。通过直接最小化不同温度下的自由能，计算了单轴和双轴取向相的序参量。得到了相应的相图，使人们能够研究单轴和双轴相的稳定区域的分子模型参数的影响。结果被用来澄清实验观察到的双轴有序的性质，在液晶的四脚分子组成的具有相同的对称性。
Relative stability of uniaxial and biaxial nematic phases is analyzed in a model nematic liquid crystal composed of flat molecules of C2h symmetry with four mesogenic groups rigidly linked to the same center. The generalized effective quadrupole mean-field potential is proposed and its constants are evaluated numerically for the pair intermolecular potential based on Gay-Berne interaction between mesogenic groups. The dependencies of the constants on molecular shape parameters are systematically analyzed. Order parameters of the uniaxial and biaxial nematic phases are evaluated by direct minimization of the free energy at different temperatures. The corresponding phase diagrams are obtained enabling one to study the effects of molecular model parameters on the stability regions of uniaxial and biaxial phases. The results are used to clarify the nature of experimentally observed biaxial ordering in nematic liquid crystals composed of tetrapode molecules with the same symmetry.