Observing the emergence of phase biaxiality in a polar smectic A system via polarised Raman spectroscopy
Observing the emergence of phase biaxiality in a polar smectic A system via polarised Raman spectroscopy
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通过偏振拉曼光谱观察极性近晶 A 系统中相双轴性的出现
DOI：
10.1039/c6tc04572c
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发表时间：
2017
影响因子：
6.4
通讯作者：
H. Gleeson
中科院分区：
文献类型：
--
作者：
Zhaopeng Zhang;S. Kaur;B. Kundu;B. K. Sadashiva;H. Gleeson
我们报告的偏振拉曼光谱，光学和介电性能的不对称的三核化合物来自3-羟基苯甲酸与长末端链在一端和硝基在其他。早期的X射线散射实验表明，部分双层近晶A相（SmAd）和部分双层双轴反铁电近晶A相（SmAdPA）的材料。介电行为，微观织构和锥光实验都明确表明，该化合物具有两个不同的阶段，与较低的温度相双轴的性质。拉曼光谱被用来确定的单轴序参数的温度演变的Δ P2 β和Δ P4 β，推导出的去极化比的分析，通过建模的芯结构的通知。测量到异常低的值（分别小于0.5和0.15），这可能表明近晶A相在性质上可能是德弗里斯样的，而不是部分双层结构。拉曼光谱也被用来调查的SmAdPA相的双轴性质。计算了双轴序参量λ P220 λ、λ P420 λ和λ P440 λ对退偏比的影响。通过假设一个近似连续的增加，在P2P和P4P的顺序参数，这是可能的推导出的行为的双轴序参数在双轴SmAdPA相;双轴顺序的出现在系统中清楚地表明，所有的双轴序参数的幅度增加，随着温度的降低（SmAdPA）相。介电性能的研究表明，SmAd相的介电常数垂直分量从10增加到70，SmAdPA相的介电常数垂直分量从70减小到45。一个强烈的温度依赖性的弛豫频率与一个大的值为400 kHz的SmAd相观察。另一方面，SmAdPA相在100 kHz处表现出弱的温度依赖性弛豫频率。
We report polarised Raman spectroscopy, and optical and dielectric properties of an asymmetric bent-core compound derived from 3-hydroxybenzoic acid with a long terminal chain at one end and a nitro group at the other. Earlier X-ray scattering experiments on the compound suggested a partial bilayer smectic A phase (SmAd) and a partial bilayer biaxial antiferroelectric smectic A phase (SmAdPA) in the material. The dielectric behaviour, the microscopic textures and conoscopy experiments all explicitly show that the compound exhibits two different phases, with the lower temperature phase biaxial in nature. Raman spectroscopy was used to determine the temperature evolution of the uniaxial order parameters 〈P2〉 and 〈P4〉, deduced from the analysis of the depolarisation ratio, informed by modelling the bent-core structure. Anomalously low values were measured (less than 0.5 and 0.15 respectively) which could suggest that the smectic A phase may be de Vries like in nature, rather than a partial bilayer structure. Raman spectroscopy was also used to investigate the biaxial nature of the SmAdPA phase. The effect that the biaxial order parameters 〈P220〉, 〈P420〉 and 〈P440〉 have on the depolarisation ratio is calculated. By making the assumption of an approximately continuous increase in the 〈P2〉 and 〈P4〉 order parameters, it was possible to deduce the behaviour of the biaxial order parameters in the biaxial SmAdPA phase; the emergence of biaxial order in the system is clearly demonstrated as all of the biaxial order parameters increase in magnitude as the temperature decreases in the (SmAdPA) phase. The dielectric studies show that the perpendicular component of the dielectric permittivity increases from 10 to 70 in the SmAd phase and decreases from 70 to 45 in the SmAdPA phase. A strongly temperature dependent relaxation frequency with a large value of ∼400 kHz is observed in the SmAd phase. On the other hand, the SmAdPA phase exhibits a weakly temperature dependent relaxation frequency at ∼100 kHz.
影响因子：
6.4
作者：
Zhaopeng Zhang;Vitaly P. Panov;M. Nagaraj;R. Mandle;J. Goodby;G. R. Luckhurst;J. C. Jones;H. Gleeson
通讯作者：
Zhaopeng Zhang;Vitaly P. Panov;M. Nagaraj;R. Mandle;J. Goodby;G. R. Luckhurst;J. C. Jones;H. Gleeson
了解暗砾岩相纳米结构的异常重组。
DOI：
10.1103/physreve.91.042504
发表时间：
2015
期刊：
Physical review. E, Statistical, nonlinear, and soft matter physics
影响因子：
--
作者：
Nagaraj M
通讯作者：
Nagaraj M
影响因子：
2.2
作者：
Gleeson, H. F.;Southern, C. D.;Gortz, V.
通讯作者：
Gortz, V.