Electronic structures of low-lying Bu excited states in trans-oligoenes: Pariser-Parr-Pople and ab initio calculations.
Electronic structures of low-lying Bu excited states in trans-oligoenes: Pariser-Parr-Pople and ab initio calculations.
复制标题
DOI：
10.1063/1.3643838
复制
发表时间：
2011-10
期刊：
影响因子：
--
通讯作者：
Dawei Zhang;Chungen Liu
中科院分区：
文献类型：
--
作者：
Dawei Zhang;Chungen Liu
采用Pariser-Parr-Pople（PPP）模型，在全组态相互作用（FCI）水平和从头算方法，计算了全反式寡烯的两个B（u）对称性最低激发单态：离子1（1）B（u）（+）态和离子-共价混合1（1）B（u）（-）态. PPP-FCI计算得到的垂直激发能和波函数与高水平多参考方法，如多参考完全活性空间自洽场（CASSCF）和二级微扰修正（CASPT 2），多参考Møller-Plesset微扰理论（MRMP）和完全活性空间价键理论（CASVB）的计算结果吻合较好.由PPP计算得到的振子强度与光谱实验符合得很好。1（1）B（u）（-）的振子强度相对较小是由于该状态的近似电子-空穴对称性。此外，两种激发态的键长与基态几何计算的键级具有显著的相关性，这为激发态几何优化中的初始猜测提供了一种可能的策略.
Two lowest-lying excited singlets with B(u) symmetry of all-trans-oligoenes, the well-known ionic 1(1)B(u)(+) state as well as the "hidden" ionic-covalent-mixed 1(1)B(u)(-) state, are calculated within both the Pariser-Parr-Pople (PPP) model at full configuration interaction (FCI) level and ab initio methods. The vertical excitation energies as well as wavefunctions from PPP-FCI calculations are found to be in good agreement with those from high-level multi-reference methods, such as multi-reference complete active space self-consistent field (CASSCF) with second order perturbative corrections (CASPT2), multi-reference Møller-Plesset perturbation theory (MRMP), and complete active space valence bond theory (CASVB). The oscillator strengths from PPP calculation are in good agreement with spectroscopy experiments. The relatively small oscillator strength of 1(1)B(u)(-) is due to the approximate electron-hole symmetry of this state. In addition, the bond lengths in both states are found to show remarkable relativity with the bond orders calculated with ground state geometries, which suggests a possible strategy for initial guess in geometry optimization of excited states.