分子超极化率作为铁电向列液晶二阶非线性光学的筛选描述符
Molecular Hyperpolarisability as a Screening Descriptor for Second-Order Nonlinear Optics in Ferroelectric Nematic Liquid Crystals
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中文总结 AI 辅助
该研究以分子超极化率为描述符，通过DFT计算和取向气体模型筛选铁电向列液晶，识别出非线性光学响应增强的候选材料并揭示相关设计规则。
中文摘要 AI 辅助
铁电向列液晶兼具流动性与宏观极性有序性。尽管原型NF材料RM734表现出大的非线性光学系数，但多数已知铁电向列液晶的设计未考虑光学非线性。本文评估电子结构计算是否可用于从已知极性液晶材料中识别有前景的非线性光学候选物。采用多种DFT方法和基组计算频率依赖的分子超极化率张量，再利用带经验<P1>和<P3>值的取向气体模型将其转换为宏观d系数。将计算值与代表性材料的现有实验d33、d15及d13/d31系数进行基准测试。研究发现，绝对值强烈依赖于方法和体参数假设，而相对趋势更适用于筛选；明确的构象平均并未始终改善与实验的一致性。将表现最佳的单构象方案应用于更广泛的极性液晶数据集，识别出具有增强预测非线性光学响应的候选材料，并揭示了基于给体-受体不对称性、共轭长度和连接基选择的简单设计规则。
英文摘要
Ferroelectric nematic liquid crystals combine fluidity with macroscopic polar order. Although the archetypal NF material RM734 exhibits large nonlinear optical coefficients, most known ferroelectric nematics were designed without consideration of optical nonlinearity. Here, we assess whether electronic-structure calculations can be used to identify promising nonlinear optical candidates within known polar liquid-crystal materials. Frequency-dependent molecular hyperpolarisability tensors were calculated using a range of DFT methods and basis sets, then converted to macroscopic d-coefficients using an oriented-gas model with empirical <P1> and <P3> values. Calculated values were benchmarked against available experimental d33, d15, and d13/d31 coefficients for representative materials. We find that absolute values depend strongly on method and bulk-parameter assumptions, whereas relative trends are more useful for screening. Explicit conformer averaging does not consistently improve agreement with experiment. Applying the best-performing single-conformer protocols to a broader polar liquid-crystal dataset identifies candidate materials with enhanced predicted nonlinear optical response and reveals simple design rules based on donor-acceptor asymmetry, conjugation length, and linker choice.
