Critical behavior at nematic-smectic-A1 phase transtions. II. Preasymptotic three-dimensional XY analysis of x-ray and Cp data.
Critical behavior at nematic-smectic-A1 phase transtions. II. Preasymptotic three-dimensional XY analysis of x-ray and Cp data.
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向列-近晶-A1 相变时的关键行为。
DOI：
10.1103/physreve.47.1918
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发表时间：
1993
期刊：
影响因子：
--
通讯作者：
R. Birgeneau
中科院分区：
文献类型：
--
作者：
Carl W. Garland;George Nounesis;M. J. Young;R. Birgeneau
报告了戊基苯基氰基苯甲酰氧基苯甲酸酯 (DB 5 CN)+氰基苯甲酰氧基戊基芪 (C 5 芪) 二元混合物中向列 (N)–近晶-A 1 (Sm-A 1) 转变附近的向列相的 X 射线数据。使用渐进前三维 (3D) XY 理论的精确解对这些数据和来自其他四个 N–Sm-A 1 系统的 X 射线数据以及相应的高分辨率 C p 数据进行了分析。相关体积 Σ∥ Σ⊥ 2、近晶磁化率 σ 和热容 C p 与渐近前的理论预测非常一致。先前已知一阶标度校正项对于描述 C p 很重要；此处展示了它们对于 Υ∥ Ψ⊥ 2 和 σ 的重要性。目前的自洽分析证实了 3D XY 模型的许多普遍特征，但个体长度 Υ∥ 和 Ψ⊥ 的临界各向异性以及 C p 表现出正常的 XY 振幅比而不是理论上预测的反转比的事实仍然是未解决的问题。
X-ray data are reported for the nematic phase near the nematic (N)–smectic-A 1 (Sm-A 1) transition in a binary mixture of pentylphenylcyanobenzoyloxy benzoate (DB 5 CN)+ cyanobenzoyloxypentylstilbene (C 5 stilbene). These data and x-ray data from four other N–Sm-A 1 systems, plus the corresponding high-resolution C p data, are analyzed using the exact solutions of preasymptotic three-dimensional (3D) XY theory. The correlation volume ξ∥ ξ⊥ 2, smectic susceptibility σ, and heat capacity C p are in good agreement with preasymptotic theoretical predictions. First-order corrections-to-scaling terms were known previously to be important for describing C p; their importance for ξ∥ ξ⊥ 2 and σ is demonstrated here. Many universal features of the 3D XY model are confirmed by the present self-consistent analysis, but the critical anisotropy of the individual lengths ξ∥ and ξ⊥ and the fact that C p exhibits a normal XY amplitude ratio rather than the theoretically predicted inverted ratio are still unresolved issues.