On the performance of DFT/MRCI-R and MR-MP2 in spin–orbit coupling calculations on diatomics and polyatomic organic molecules
On the performance of DFT/MRCI-R and MR-MP2 in spin–orbit coupling calculations on diatomics and polyatomic organic molecules
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DOI：
10.1080/00268976.2016.1201600
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发表时间：
2017-01
影响因子：
1.7
通讯作者：
V. Jovanović;I. Lyskov;M. Kleinschmidt;C. Marian
中科院分区：
文献类型：
--
作者：
V. Jovanović;I. Lyskov;M. Kleinschmidt;C. Marian
摘要 我们研究了不同多参考量子化学方法在电子激发能和自旋轨道矩阵元素（SOMES）方面的性能。这些方法包括组合密度泛函理论和多参考构型交互方法（DFT/MRCI 和 DFT/MRCI-R）和多参考二阶 Møller-Plesset 微扰理论（MR-MP2）方法的两种变体。 MR-MP2 的两种变体已经基于 BH-LYP 密度泛函的 Hartree-Fock 轨道或 Kohn-Sham 轨道进行了测试。结合 MR-MP2 方法，一阶扰动波函数已用于评估自旋轨道耦合。为了验证我们的结果，我们组装了八个双原子和十五个多原子分子的实验激发能和 SOMES。对于一些较小的分子，我们在完全活性空间自洽场（CASSCF）水平上进行计算，以获得一些可比较的分子。实验未知状态的激发能根据二阶微扰理论校正（CASPT2）值（如果可用）进行评估。总的来说，我们发现激发能和用四种方法获得的 SOME 之间非常令人满意。对于一些状态，观察到关于激发能和/或某些ME的异常值。这些异常值经过仔细分析并追溯到波函数组成。
ABSTRACT We have investigated the performance of different multi-reference quantum chemical methods with regard to electronic excitation energies and spin–orbit matrix elements (SOMES). Among these methods are two variants of the combined density functional theory and multi-reference configuration interaction method (DFT/MRCI and DFT/MRCI-R) and a multi-reference second-order Møller–Plesset perturbation theory (MR-MP2) approach. Two variants of MR-MP2 have been tested based on either Hartree–Fock orbitals or Kohn–Sham orbitals of the BH-LYP density functional. In connection with the MR-MP2 approaches, the first-order perturbed wave functions have been employed in the evaluation of spin–orbit coupling. To validate our results, we assembled experimental excitation energies and SOMES of eight diatomic and fifteen polyatomic molecules. For some of the smaller molecules, we carried out calculations at the complete active space self-consistent field (CASSCF) level to obtain SOMEs to compare with. Excitation energies of the experimentally unknown states were assessed with respect to second-order perturbation theory corrected (CASPT2) values where available. Overall, we find a very satisfactory agreement between the excitation energies and the SOMEs obtained with the four approaches. For a few states, outliers with regard to the excitation energies and/or SOMEs are observed. These outliers are carefully analysed and traced back to the wave function composition.