基于Pariser-Parr-Pople模型的低对称性多环Aromatic Hydrocarbon分子线性光吸收的相互作用研究
Pariser-Parr-Pople Model based Configuration-Interaction Study of Linear Optical Absorption in Lower-Symmetry Polycyclic Aromatic Hydrocarbon Molecules
摘要：
多环芳烃的电子和光学性质（多环芳烃）具有较低的对称性，即，苯并[ghi]二萘嵌苯（C $_{22}$ H $_{12}$），苯并[a]蔻（C $_{28}$ H $_{14}$），萘并[2，3a]晕苯（C $_{32}$ H $_{16}$），蒽[2，3a]晕苯（$_{36}$-$_{18}$）和萘并[8，1，研究了[α 2-abc]晕苯（C $_{30}$ H $_{14}$）。为此，我们进行了电子相关计算使用屏蔽，和标准参数的$π$ -电子Pariser-Parr-Pople（PPP）哈密顿量，并包括相关效应，无论是基态和激发态，使用多参考单双组态相互作用（MRSDCI）的方法。PPP模型的哈密顿量包含了长程库仑相互作用，这增加了我们计算的准确性。计算结果表明，随着并苯衍生物尺寸的增大，其光谱发生红移，光学带隙减小。在每个光谱中，代表光学带隙的第一个峰具有中等强度，而更强的峰出现在更高的能量处。我们的计算光谱与现有的实验数据吻合得很好。为了比较，我们还使用高斯基函数对这些分子的光学带隙进行了第一性原理含时密度泛函理论（TDDFT）计算，发现它们产生的值低于我们的CI结果。
英文摘要：
The electronic and optical properties of various polycyclic aromatic hydrocarbons (PAHs) with lower symmetry, namely, benzo[ghi]perylene (C$_{22}$H$_{12}$), benzo[a]coronene (C$_{28}$H$_{14}$), naphtho[2,3a]coronene (C$_{32}$H$_{16}$), anthra[2,3a]coronene (C$_{36}$H$_{18}$), and naphtho[8,1,2-abc]coronene (C$_{30}$H$_{14}$) were investigated. For the purpose, we performed electron-correlated calculations using screened, and standard parameters in the $π$-electron Pariser-Parr-Pople (PPP) Hamiltonian, and the correlation effects were included, both for ground and excited states, using the multi-reference singles-doubles configuration-interaction (MRSDCI) methodology. PPP model Hamiltonian includes long-range Coulomb interactions, which increase the accuracy of our calculations. The results of our calculations predict that, with the increasing sizes of the coronene derivatives, optical spectra are red shifted, and the optical gaps decrease. In each spectrum, the first peak representing the optical gap is of moderate intensity, while the more intense peaks appear at higher energies. Our computed spectra are in good agreement with the available experimental data. For the purpose of comparison, we also performed first-principles time-dependent density-functional theory (TDDFT) calculations of the optical gaps of these molecules using Gaussian basis functions, and found that they yielded values lower than our CI results.
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