Quantum Chemistry Research On Polycyclic Aromatic Compound

Polycyclic Aromatic Compound (PAHs) is a kind of high priority contamination, and there is signifanct importance in researchig the reaction between the PAHs and Hydrobromic acid (a typical Hunic Acid). Gaussian 03 software is use to do research and calculation in this dissertation. The author compared the differences of the Ab initio Methods (Hartree-Fock Model, HF) , Mφller-Plesset Theory and Density Funtional Theory Method which were used in calculating the character of PAHs. The effects of the Split Valence Basis Sets(6-31G), Polarized Basis Sets(6-31 G(d)) and Polarized Basis Sets(6-31G(d, p)) Molecular bonding mechanis in Phenanthrene and Hydrobromic acid are discussed. It was noted that HF/6-31G(d) method is best method, being the most consistent with experimental data.The results indicate:(1) Polarized Basis Sets of 6-31G(d) and 6-31G(d,p) are both capable of structural optimization and Electronic Spectrum calculation is consistent with experimental data, while 6-31G(d) is less expensive. HF model and Moller-Plesset Theory (MP2) both get analogous Electronic Spectrum results. The Infared Spectrum calculation error maybe 6.1%, with calculation cost no more than 10 hours. The calculated data of molecular orbitals makes the results clear. We also found Infared spectra and Raman spectra caculated are consistent with experimental data.(2) The front orbital constitution of the molecule in the Electronic Spectrum basically participates in the conjugate carbon atom 2p_z and the 3p_z orbitals. And four potential existing structures were obtained.(3) The contrast between the phenanthrene, the benformyl acid infrared spectrum and the Raman spectrum theoretical calculation vibration frequency and the experimental value indicates that HF/6-31G(d) infrared computation, the Raman spectrum is basically consistent with the experiment. Moleculer orbital calculation can well illustrate experimental results and electron spectrums. And Infrared Spectrum coincides very well with the experimental results. (4) The kind of pyrene link aromatic hydrocarbon Raman spectrum activity is quite strong.