Acharya Bharat R, Kang Shin-Woong, Prasad Veena, Kumar Satyendra
Platypus Technologies, 5520 Nobel Drive, Madison, Wisconsin 53705, USA.
J Phys Chem B. 2009 Mar 26;113(12):3845-52. doi: 10.1021/jp810333r.
X-ray diffraction is one of the most definitive methods to determine the structure of condensed matter phases, and it has been applied to unequivocally infer the structures of conventional calamitic and lyotropic liquid crystals. With the advent of bent-core and tetrapodic mesogens and the discovery of the biaxial nematic phase in them, the experimental results require more careful interpretation and analysis. Here, we present ab-initio calculations of X-ray diffraction patterns in the isotropic, uniaxial nematic, and biaxial nematic phases of bent-core mesogens. A simple Meier-Saupe-like molecular distribution function is employed to describe both aligned and unaligned mesophases. The distribution function is decomposed into two, polar and azimuthal, distribution functions to calculate the effect of the evolution of uniaxial and biaxial nematic orientational order. The calculations provide satisfactory semiquantitative interpretations of experimental results. The calculations presented here should provide a pathway to more refined and quantitative analysis of X-ray diffraction data from the biaxial nematic phase.
X射线衍射是确定凝聚态相结构最具权威性的方法之一，它已被用于明确推断传统棒状和溶致液晶的结构。随着弯曲核和四足介晶的出现以及其中双轴向列相的发现，实验结果需要更仔细的解释和分析。在此，我们给出了弯曲核介晶在各向同性、单轴向列相和双轴向列相中的X射线衍射图案的从头计算。采用一个类似于迈尔-绍佩的简单分子分布函数来描述取向和未取向的中间相。该分布函数被分解为两个分布函数，即极向分布函数和方位角分布函数，以计算单轴和双轴向列取向序演化的影响。这些计算为实验结果提供了令人满意的半定量解释。本文所做的计算应为更精确和定量分析来自双轴向列相的X射线衍射数据提供一条途径。
