Distribution functions in three liquid crystals from X-ray diffraction measurements
Distribution functions in three liquid crystals from X-ray diffraction measurements
复制标题
X 射线衍射测量的三种液晶的分布函数
DOI：
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发表时间：
1979
期刊：
影响因子：
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通讯作者：
E. Norris
中科院分区：
文献类型：
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作者：
A. Leadbetter;E. Norris
用摄影方法测量了三种化合物在不同温度下的X射线散射强度。所研究的物质为向列相和近晶相的4，4‘-二正辛氧基偶氮苯(OOAB)及其二正庚基同系物(HOAB)和向列相和近晶相的4-(4’-乙酰氧基亚甲基)氨基肉桂酸乙酯(EABAC)。在所有情况下，除了HOAB的近晶C相外，都确定了描述≳-10分子团簇的局域指向矢相对于平均指向矢取向的分布函数fd(Fd)。Fd(β)的形式接近于简单平均场理论所预测的形式，尽管有序参数⟨、P2、⟩的大小总体上有很大的不同。从简单的平均场值。结果表明，fd(β)更接近于真实的单线态分布，因此占主导地位的角涨落是协同的，涉及多个分子。对于近晶层分布的密度波f(Z)的近晶相性质进行了研究。
The intensities of X-ray scattering from three compounds has been measured photographically at a number of temperatures. The substances studied were 4,4′di-n-octyloxyazoxybenzene (OOAB) and its di-n-heptyl homologue (HOAB) in their nematic and smectic C phases and ethyl-4-(4′acetoxybenzylidene)aminocinnamate (EABAC) in its nematic and smectic A phases. In all cases except the smectic C phase of HOAB the distribution function f d(β) describing the orientation of the local director for clusters of ≳ 10 molecules relative to the average director has been determined. The form of f d(β) is close to that predicted by simple mean field theory although the magnitude of the order parameters ⟨P 2⟩ in general differ significantly. from the simple mean field values. The results suggest that f d(β) is close to the true singlet distribution so that the dominant angular fluctuations are co-operative and involve several molecules. For the smectic phases properties of the density wave f(z) which is the smectic layer distr...