胸腺嘧啶分子表面增强拉曼光谱的密度泛函理论和从头计算研究

采用量子化学B3LYP(含电子相关效应的杂化密度泛函)方法和HF(Hartree-Fock, 哈特利-福克)方法，在6-31+G**(C，H，N，O)/LANL2DZ(Ag)水平上，对TH(Thymine, 胸腺嘧啶)分子进行了几何结构优化，计算了TH分子的NRS(normal Raman scattering, 常规拉曼散射)光谱和TH与Ag原子以及Ag₂团簇吸附的SERS(surface-enhanced Raman scattering, 表面增强拉曼散射)光谱，并将两种理论方法计算的结果和实验值进行比较。结果表明：对于NRS光谱，采用DFT方法的计算结果比HF方法的计算结果更符合已有实验值;而对于SERS光谱，采用HF方法的计算结果更好。最后，通过GaussView可视化软件，对TH分子的振动频率进行了更为全面地归属。

Surface-Enhanced Raman Spectra of Thymine Calculated by DFT and ab Inition HF

In the present paper, B3LYP (Becke’s three-parameter hybrid method with the Lee, Yang, and Parr gradientcorrected correlation functional) and HF (Hartree-Fock) methods at 6-31+G**(C，H，N，O)/LANL2DZ(Ag) level were used to optimize molecular configurations of thymine. Base on the optimized structure, the normal Raman spectrum (NRS) of thymine and the surface-enhanced Raman spectrum (SERS) of thymine adsorbed on Ag and Ag₂ were calculated, which were compared with the experimental values. The calculation results indicated that the result of the DFT for NRS was more approximate to the ever reported experimental date than those of HF results. A better conformity of SERS was found between the HF computed and the experimental results. At the end, detailed analysis of the Raman spectrum and more comprehensive assignments of the vibration mode for thymine were studied by the software of GaussView.