Sancho-García J C, Pérez-Jiménez A J
Departamento de Química Física, Universidad de Alicante, Alicante, Spain.
Phys Chem Chem Phys. 2008 May 7;10(17):2308-15. doi: 10.1039/b719080h. Epub 2008 Mar 6.
The theoretical challenge of finding a single method that quantitatively reproduces both the experimental low-lying excitation energies and the torsional barrier of a prototypical conjugated molecule, which could act as a molecular wire, has been addressed here. The results indicate that this goal can be reasonably achieved when multi-reference perturbation theory up to second order (MRMP2) based on a complete active space self-consistent field (CASSCF) wave function using large active spaces is used. The results obtained were also used to compare with less expensive Kohn-Sham (KS) density functional theory (DFT) calculations when applied to these properties. The results obtained with BLYP and B3LYP exchange-correlation functionals indicate that quantitative agreement with all the experimental data cannot be obtained with this methodology, with a clear dependence on the exchange-correlation form selected. We thus encourage a careful testing of pure and hybrid density functionals whenever KS DFT is used for the rational design of conjugated materials for charge conduits.
本文探讨了寻找一种单一方法的理论挑战，该方法能够定量再现典型共轭分子（可作为分子导线）的实验低激发能和扭转势垒。结果表明，当使用基于大活性空间的完全活性空间自洽场（CASSCF）波函数的二阶多参考微扰理论（MRMP2）时，这一目标能够合理实现。所得结果还用于与应用于这些性质时成本较低的Kohn-Sham（KS）密度泛函理论（DFT）计算进行比较。使用BLYP和B3LYP交换相关泛函获得的结果表明，该方法无法与所有实验数据达成定量一致，且明显依赖于所选的交换相关形式。因此，我们鼓励在使用KS DFT进行共轭电荷传导材料的合理设计时，仔细测试纯密度泛函和杂化密度泛函。
