The Molecular Design Of Nonlinear Optical Materials And Quantum Chemical Study

The nonlinear optical (NLO) susceptibilities of 1-amino-4-nitrol,3-butadiene have been calculated by coupled-perturbation Hartree-Fork (CPHF),finite field (FF) and time-depended Hartree-Fork (TDHF) methods at ab initio Hartree-Fork (HF),Moller-Plesset second-order perturbation (MP2) and Density Functional Theory (B3LYP) theoretical levels. The calculated results are sensitive to effects of basis sets, electronic correlation and dispersions. The optimized geometries at the same level (HF,MP2 or B3LYP) with different basis sets exert relatively small effect on results, whereas the optimized geometries at different level (HF,MP2 or B3LYP) with different basis sets are very sensitive to the calculated results. When including the electron correlation, the hyperpolarabilities calculated at MP2 level are 2-3 times the values calculated at HF level with the same basis sets. Through the optimization of basis sets, 6-31+G* basis set at B3LYP level is desirable with less calculation but sound results. The dispersion curve for 1-anino-4-nitro-1, 3-butadiene over the range of 730-2479 Inm is given by ab initio with TDHF method.The NLO susceptibilities of a series of D-n-A-typed polyethylene have been studied at ab initio HF/6-31G* level. The results show that hyperpolarabilities increase with the increasing degrees of polymerization. When the degree of polymerization is equal 10,the hyperpolarabilitie begins to reduce. This is the predicted saturation length.The NLO susceptibilities of a series of push-pull 1,3,5-hexatiene molecules designed have been calculated by CPHF method at ab initio level. The effects of molecular structure, substituent number, substituent position, conjugated length, trans-or cis- molecular structures, donor and acceptor on the hyperpolarbility P have been studied. At last a new NLO material molecule 18 with 5 substituents has bigger Pvec ,which is 699.5% of molecule 1 with one donor (NH2), 528.8% of molecule 2 with one acceptor (NO2), 181.8% of molecule 3 with one donor (NH2) and one acceptor (NO2). Our results only analyze from the theretical aspect .The results need to confirm by the experiments.