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首页> 外文期刊>The Journal of Chemical Physics >Electron correlation effects on the first hyperpolarizability of push-pull-π-conjugated systems
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Electron correlation effects on the first hyperpolarizability of push-pull-π-conjugated systems

机译：电子相关性对推挽π共轭体系的第一超极化性的影响

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The first hyperpolarizability () of representative push-pull-conjugated compounds has been calculated at several levels of approximation to assess the effects of electron correlation. First, the 6-31G(d) basis set has been shown to give the best balance between accuracy and computational resources for a polyene linker whereas for polyyne linker, the 6-31G(d) basis set is already an optimal choice. As a result of cancellations between higher order contributions, the MP2 method turns out to be the method of choice to predict of push-pull-conjugated systems since it closely reproduces the values obtained with the reference CCSD(T) scheme. Moreover, the SDQ-MP4 and CCSD approaches provide rarely improved estimates over MP2 while the MP4 method does not represent an improvement over MP4-SDQ or the SCS-MP2 method, over MP2. Among density functional theory exchange-correlation functionals, LC-BLYP is reliable when characterizing the changes of first hyperpolarizability upon enlarging the-conjugated linker or upon changing the polyyne linker into a polyene segment. Nevertheless, its reliability is very similar to what can be achieved with the Hartree-Fock method and the MP2 scheme is by far more accurate. On the other hand, the BLYP, B3LYP, and BHandHLYP functionals perform quantitatively better in a number of cases but the trends are poorly described. This is also the case of the B2-PLYP and mPW2-PLYP functionals, which are often the most accurate, though they underestimate the increase of when going from polyyne to polyene linkers and overestimate the enhancement of with chain length.
机译：代表推挽共轭化合物的第一个超极化率（）已在几种近似水平上进行了计算，以评估电子相关性的影响。首先，已经证明6-31G（d）基组在多烯连接基的准确性和计算资源之间达到了最佳平衡，而对于多炔连接基，6-31G（d）基组已经是最佳选择。由于取消了高阶贡献，因此MP2方法成为预测推挽共轭系统的首选方法，因为它紧密地再现了通过参考CCSD（T）方案获得的值。此外，SDQ-MP4和CCSD方法几乎无法提供比MP2更好的估计，而MP4方法并不代表比MP4-SDQ或SCS-MP2方法要优于MP2。在密度泛函理论交换相关泛函中，当表征共轭连接基或将多炔连接基变为多烯链段时第一超极化性的变化时，LC-BLYP是可靠的。但是，其可靠性与使用Hartree-Fock方法可以实现的可靠性非常相似，并且MP2方案要精确得多。另一方面，在许多情况下，BLYP，B3LYP和BHandHLYP功能在定量上表现更好，但趋势描述得很差。 B2-PLYP和mPW2-PLYP官能团也是这种情况，它们通常是最准确的，尽管它们低估了从多炔到多烯连接子时的增加，并高估了链长的增加。

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