聚合物非线性光学材料

最近,有机非线性光学材料已引起了人们极大的兴趣。一些可极化有机分子具有很大的分子超极化率,可惜,受晶体对称性的限制仅有少数晶体具有二阶非线性光学效应。极化聚合物可以产生统计非中心对称的环境,使材料的二阶特性显示出来。本文在简单介绍了有机非线性光学和极化的原理后,综述了聚合物二阶非线性光学材料的研究进展。此外,对聚合物的三阶非线性光学效应的研究也作了介绍。     

三核欠完整立方烷金属原子簇二阶非线性光学性质的理论研究

研究了具有欠完整立方烷构型的过渡金属原子簇分子的二阶非线性光学性质。利用TDDFT方法计算了选取的簇分子及相应模拟构造分子的静态和动态的一阶非线性光学超级化率(ijk);并计算了不同金属、桥原子和配体以及簇芯对该类化合物一阶超级化率的影响。选取其中的一个簇分子为基本模型,分析了该分子的电子结构和分子轨道,在微观水平上阐述了其非线性光学性质的可能起源。认为由过渡金属和硫原子组成的簇芯和与桥原子相连的配体对该类簇合物的二阶非线性光学性质的起决定性的作用。     

聚脲分子的非线性光学极化率

用ａｂ　ｉｎｉｔｉｏ／ＣＰＨＦ方法研究了尿素及其二聚体和三聚体分子的线性极化率,一阶超极化率和二阶超极化率．聚脲分子中含有多个交替排列的供电基和吸电基．计算发现,聚二脲和聚三脲较尿素具有更大的非线性光学极化系数,且其电荷分布具有新的特点,即聚脲分子由基态到激发态电荷并不发生分子范围内的长程传递,仅在局域内转移．     

过渡金属类立方烷原子簇化合物电子结构和二阶非线性光学性质的密度泛函理论研究

采用基于第一原理的含时密度泛函理论(TDDFT)对一系列具有类立方烷簇芯结构的过渡金属簇合物二阶非线性光学性质进行了研究。结果证明, 由于簇芯结构的对称性的影响, 这一类簇分子的二阶非线性光学系数的数值要小于三核欠完整类立方烷体系。通过对电子结构的分析, 发现二阶非线性光学性质主要是由簇芯内电荷的迁移造成的。轨道分析显示, -S原子对于电荷的迁移起主要的传递作用。定域化轨道分析证明簇分子中存在的多中心键有利于簇芯内电荷的迁移。分子模拟的研究表明:虽然类立方烷结构簇分子的值比较小, 但是通过合理的配体设计, 获得具有较大值非线性光学晶体是可能的。     

溶致变色法测定Schiff碱类化合物非线性二阶极化率张量分量β~xxx和估算二阶极化率向量分量β~x

提出了一个以二能级模型为基础,结合溶致变色法计算非线性光学分子二阶极化率向量分量β_x的新方法.使用溶致变色法测定了新的Schiff碱化合物的二阶极化率张量分量β_(xxx),并对其非线性光学特性进行了评估.     

一类五核平面开口型过渡金属原子簇电子吸收光谱和二阶非线性光学性质的TDDFT研究

运用TDDFT B3LYP/LanL2DZ方法, 研究了一类具有非中心对称的五核平面开口构型过渡金属原子簇化合物[MoS₄Cu₄(py)₆X₂] (X＝Br, I)的电子吸收光谱和静态二阶非线性极化率, 估算了晶体的宏观二阶非线性光学系数. 电子吸收光谱的计算结果与实验测量结果比较符合; 碘系簇合物的静态二阶非线性极化率大于溴系. 详细讨论了该类金属簇合物电子吸收光谱的归属及其相关联的电子跃迁方式; 在微观水平上阐述了其二阶非线性光学性质的起源. 研究结果表明外围无机卤素配体4p/5p轨道到簇芯[MoS₄]杂化轨道的电子转移对静态二阶非线性极化率的贡献大于有机配体的贡献; 而过渡金属簇芯内的电子转移也有较大的贡献. 这对于理解过渡金属原子簇化合物内的电子转移对光学激发的作用以及用来设计新的无机-有机杂化二阶非线性光学材料有较大的帮助.     

溶致变色法测定Schiff碱类化合物非线性二阶极化率张量分量β~xxx和估算二阶极化率向量分量β~x

提出了一个以二能级模型为基础, 结合溶致变色法计算非线性光学分子二阶极化率向量分量β~x的新方法, 使用溶致变色法测定了新的Schiff碱化合物的二阶极化率张量分量β~xxx, 并对其非线性光学特性进行了评估。     

新型苯并噻二唑衍生物的非线性光学性质理论研究

以苯并噻二唑分子为母体,设计了5个系列的衍生物,采用AM1半经验量子化学方法,研究了共轭π桥的不同增长方式和不同推拉电子基团对分子的电子结构及非线性光学性质的影响.结果表明:共轭链较短时,分子的二阶极化率和三阶极化率与共轭链长的线性相关性较好;而当共轭链较长时,分子的二价极化率和三阶极化率随着共轭链的增长而呈起伏性变化;与三氰基呋喃相比,三硝基呋喃对非线性极化率的影响更大;部分目标分子的一阶极化率α与Δμ·ΔE-1、二阶极化率β与α·ΔE-1、三阶极化率γ与α·ΔE-2和β·ΔE-1都有较好的相关性.     

非线性光学极化率密度泛函理论计算的基组效应

由于分子的非线性光学性质与分子外层电子行为及激发性质密切相关,扩散函数对分子的非线性光学极化率计算非常重要.在ADF程序中的DZP基组基础上缀加扩散函数,构造出我们称之为DZP+df的新基组.通过对5个模型分子的含频二阶非线性光学极化率的密度泛函理论计算,表明新基组可以得出较DZP基组更为准确可靠的结果,同时比较ADF程序内置带有扩散函数的大基组,计算量大为减少.     

一水甲酸锂晶体二阶非线性光学系数的理论计算

采用有限场方法和含时耦合微扰方法,在6-31+G*基组水平上并考虑了电子相关效应和色散效应的影响,计算了一水甲酸锂晶体的宏观二阶非线性光学极化率和二阶非线性光学系数。其中非线性光学系数d31和d32与Roberts报道的相符,而另一个系数d33则比文献值大。计算结果还表明,在非共振情况下,电子相关效应对非线性光学极化率的影响远远超过了色散效应,同时表明Roberts报道的非线性光学系数比Singh等人报道的更为合理。     

Cooperative interactions in supramolecular aggregates: linear and nonlinear responses in calix[4]arenes.

The linear and nonlinear optical polarizabilities of donor-acceptor (D-pi-A) chromophores in confined geometries of calix[4]arenes are investigated through a model for interacting polar-polarizable molecules. Both the linear polarizability (alpha) and the first hyperpolarizability (beta) decrease with increasing the interdipolar angle, as expected in the oriented-gas picture. However, within the polar-polarizable model we predict deviations from the additive result, irrespective of the interdipolar angle. Depending on the nature of the chromophore, electrostatic intermolecular interactions between polar and polarizable chromophores lead to cooperative damping or enhancement of the optical responses. Specifically, for chromophores whose ground state is dominated by the neutral D-pi-A structure both alpha and beta are suppressed with respect to the prediction of the oriented-gas model, whereas the opposite holds true for chromophores whose ground state is dominated by the zwitterionic D(+)-pi-A(-). These results explain recent experimental data on a calix[4]arene functionalized with a donor-acceptor dye for nonlinear optical applications. Density functional theory calculations on the relevant crystal structure further support our interpretation.     

尿素晶体介电性能的量子化学计算

利用量子化学的第一性原理,在自洽场理论水平上对尿素晶体的线性和非线性光学介电性质进行了定量计算,获得了与实验值相符的理论计算结果.提供了一种解决分子晶体量子化学理论计算的新思路.     

一水甲酸锂晶体三阶非线性光学性质理论研究

用含时藕合微扰Hartrre一Fork（CPHF）方法，有限场MP2理方法以及有向气 体方法，首次分别在分子和晶体水平上计算了一水甲酸锂晶体三次谐波极化率，表 明超分子γ(一3ω；ω,ω,ω)数值与超分子链长有线性关系；晶体x（一3ω;ω, ω,ω）计算值主要受到电子相关影响，其次受到基组和局域场影响，在非共振 条件下，频率色散的影响甚小'最后，估算了一水甲酸锂的三次谐波系数．     

物质材料的结构预测和光物理性能模拟

具有良好性能的非线性光学材料的成功设计,关键问题在于材料晶体结构和分子结构的可信和有效的预测结果,继而对获得结构信息的材料开展光物理性能计算模拟,这种结构预测与性能模拟结合的方法,为新材料的成功制备创出一条又省时又经济的路子。本文中,我们使用Oganov等发展的全局搜索进化算法的晶体结构预测工具(USPEX软件),成功地预测具有中远红外区透过的二阶非线性光学材料Ba2BiInS5的晶体结构;介绍应用DFT方法优化和预测内嵌富勒烯C2@Sc4@C80-Ih和Sc4C2@C80-Ih分子结构。在结构预测和优化基础上,应用基于态叠加原理(SOS)自行创建的BGP软件与计算激发态性质的软件结合,计算模拟分子晶体、纳米结构分子、生物蛋白分子等体系频率相关和态相关的非线性光学性质(包括不同光学过程的二阶、三阶极化率以及双光子、三光子吸收截面)。此外,还报道了利用固体能带理论与反谐振子模型结合,计算模拟部分离子晶体的二阶和三阶非线性光学性质。     

金属硫氰酸根配合物FeHg(SCN)_4,MnHg(SCN)_4的合成、晶体结构与非线性光学性质的研究

合成了配合物晶体FeHg(SCN)_4和MnHg(SCN)_4用单晶X射线衍射方法测定了这两个晶体的结构.以尿素为标准样品用粉末晶体倍频1064nm的Nd:YAG激光,测得其倍频光强度分别为:FeHg(SCN)_4,0.6倍于尿素;MnHg(SCN)_4,50倍于尿素.后者显示了作为新的非线性光学材料的发展前景.     

Density of states plots for hydrogen bonded crystals: Results for formamide,formic acid and urea crystals

Density of state plots are reported for the formamide, formic acid and urea crystals. It is found that the hydrogen bonding within the crystal lattice strongly disperses some molecular levels while leaving others relatively unaffected. It is suggested that this may provide means whereby ESCA could be used to investigate hydrogen bonding in crystals.     

Persulfurated aromatic compounds

Persulfurated arenes have been known for about 50 years but they were underexploited in chemistry in spite of facile, mild, and high-yielding syntheses. Their properties (redox potentials, UV/Vis absorption, conductivity, nonlinear optical properties, etc.) are mainly due to the aromaticity of the ring with sp2-hybridized carbon atoms and to the electronic contribution from numerous divalent sulfur ligands, which also stabilize negative or positive charges. The characteristic conformational patterns of the sulfur ligands often facilitate preorganization in supramolecular assemblies, with or without thiophilic metal cations, for designing redox sensors, ion-selective membranes, clathrates, organic conductors, nonlinear optical materials, liquid crystals, coordination polymers, and bioinorganic systems. A new class of supramolecules with various molecular shapes such as asterisks, chains, wheels, and windmills were reported.     

A comparative study of key properties of glycine glycinium picrate (GGP) and glycinium picrate (GP): A combined experimental and quantum chemical approach

Using experimental and computational techniques, a comparative study of electro-optical properties for glycine glycinium picrate (GGP) and glycinium picrate (GP) compounds has been performed. The single crystal of GGP has been grown using slow evaporation technique that was further subjected to experimental characterization of its electro-optical properties. The good optical transparency and mechanical strength at micro level was confirmed from optical and nanoindentation measurements using the Oliver–Pharr method of the grown single crystals. Differential scanning calorimetric (DSC) analysis was done to probe the thermal stability of the grown single crystals. Using the density functional theory (DFT) methods, we have not only investigated the GGP but also proposed GP molecule. Additionally, we have shed light on the molecular geometries, infrared and Raman spectra, linear and nonlinear optical properties of both GGP and GP at molecular level. The time dependent DFT (TD-DFT) approach was adopted to calculate the excitation energies of the molecules in different phases including gas, water, acetone, cyclohexane and chloroform as well. For GGP, its wavelength of maximum absorption is calculated to be ～390 nm at B3LYP/6-31G¹ level of theory. The calculated amplitudes of first hyperpolarizability (β_tot) for GGP and GP are found to be 712 and 970 a. u., respectively, which are about 16 and 23 times larger than that of the urea molecule (a prototype NLO molecule). Thus the present study not only brings to limelight the optical and nonlinear optical properties of GGP but also sheds light on the possible potential of GP as new NLO molecule.     

4, 5-二(2', 4'-二硝基苯硫基)-1, 3-二杂环戊烯-2-酮(BNPT-DTO), 4, 5-二(2', 4'-二硝基苯硫基)-1, 3-二杂环戊烯-2-硫酮(BNPT-DTT)分子及晶体激光倍频性质的理论研究

在ZINDO方法的基础上, 按完全态求和公式编制了计算分子的二阶非线性光学系数张量元βijk的程序, 并以此为基础计算了BNPT-DTO, BNPT-DTT分子二次谐波条件下的二阶非线性光学系数, 从分子水平研究了其分子的光学倍频性质及分子倍频与晶体宏观倍频的关系, 计算结果较好地说明了实验现象。     

Large second-order optical nonlinearities of s-triazine derivatives: View from micro molecules to macro crystals

Organic nonlinear optics (NLO) is also called mo-lecular nonlinear optics. In recent years organic mate-rials have been intensively studied because of their large NLO coefficients and structural diversities[1―3]. Second harmonic generation (SHG) is a bas…