溶剂中一、二维电荷转移分子二阶非线性光学性质理论研究

Theoretical study of the second-order nonlinear optical properties of one- and two-dimensional charge transfer molecules in solvents

以典型的一、二维电荷转移分子,对硝基苯胺(pNA),1,3-二氨基-4,6-二硝基苯(DADB)分子为例,运用密度泛函理论(DFT)B3LYP和含时耦合微扰(TDHF)方法在6-31+G(d,p)水平上研究了溶剂和入射光频率对目标分子的非线性光学性质的影响.研究发现溶剂分子对分子一阶超极化率β和紫外吸收光谱的影响很大,但对一阶超极化率各向异性比η和退偏比D的影响很小,这是由于随着溶剂相对介电常数的增加,一阶超极化率的分量︱βxxy︱和︱βyyy︱不断增加,且二者具有很好的线性相关性.然而,考虑色散效应后,不同溶剂中分子的一阶超极化率及其各向异性参数都不相同,色散效应对分子一阶超极化率及其各向异性性质均有很大影响.考虑溶剂效应和色散效应后得到的计算结果与实验结果符合得较好.

The solvent-dependent and frequency-dependent nonlinear optical （NLO） properties of one-dimensional charge transfer （1DCT） molecule, p-nitroaniline （pNA） and two-dimensional charge transfer （2DCT） molecule, 1,3-diamino-4,6- dinitrobenzen （DADB） have been studied by using the density functional theory （DFT） and time-dependent coupled perturbed Hartree-Fork （TDHF） method, respectively. The reasons of the influence of the solvent polarity and incident light frequency on the NLO properties for 1DCT and 2DCT molecules were also discussed. Theoretica lresults demonstrate that the first hyperpolarizability β and ultraviolet spectra strongly depend on the dielectric constant ε of solvent, but solvent polarity has little effect on the anisotropy ratio η and depolarization ratio D due to the linear relationship between ︱β_xxy︱ and ︱β_yyy︱ with the increase of the solvent dielectric constant ε. In addition, the incident frequency has a great influence on β, η and D . It is found that the solvent effect and the frequency dispersion effect should be considered in calculations for obtaining accurate results.