Efficient multireference perturbation theory without high-order reduced density matrices
Efficient multireference perturbation theory without high-order reduced density matrices
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DOI：
10.1063/5.0023353
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发表时间：
2020-10-28
影响因子：
4.4
通讯作者：
Sharma, Sandeep
中科院分区：
文献类型：
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作者：
Blunt, Nick S.;Mahajan, Ankit;Sharma, Sandeep
我们提出了一种执行强收缩n电子价态微扰理论(SC-NEVPT)的随机方法，它只需要一体和二体约化密度矩阵，而不需要引入近似。尽管这种方法适用于更大类的波函数，包括轨道-空间变分蒙特卡罗的波函数，但我们仍然使用这种方法对由所选组态相互作用得到的完全活动空间自洽场波函数进行SC-NEVPT2。在小型测试系统中验证了该方法的准确性，并用虚拟轨道数和分子大小考察了标度。我们还发现SC-NEVPT2能量对参考波函数的质量相对不敏感。最后，将该方法应用于具有(32E，29O)活性空间的Fe(II)-卟啉体系和具有(28E，32O)活性空间的[Cu2O2]2+的异构化反应。
We present a stochastic approach to perform strongly contracted n-electron valence state perturbation theory (SC-NEVPT), which only requires one- and two-body reduced density matrices, without introducing approximations. We use this method to perform SC-NEVPT2 for complete active space self-consistent field wave functions obtained from selected configuration interaction, although the approach is applicable to a larger class of wave functions, including those from orbital-space variational Monte Carlo. The accuracy of this approach is demonstrated for small test systems, and the scaling is investigated with the number of virtual orbitals and the molecule size. We also find the SC-NEVPT2 energy to be relatively insensitive to the quality of the reference wave function. Finally, the method is applied to the Fe(II)-porphyrin system with a (32e, 29o) active space and to the isomerization of [Cu2O2]2+ in a (28e, 32o) active space.