论文标题
有效的多重扰动理论，没有高阶降低密度矩阵
Efficient multireference perturbation theory without high-order reduced density matrices
论文作者
论文摘要
我们提出了一种随机方法，可以执行强大收缩的N电子价态扰动理论（SC-NEVPT），该理论仅需要一个和两体降低的密度矩阵，而无需引入近似值。我们使用此方法对从所选配置相互作用获得的CASSCF波函数进行SC-NEVPT2，尽管该方法适用于较大类的波函数，包括各种蒙特卡洛（VMC）。对于小型测试系统，证明了这种方法的准确性，并使用虚拟轨道和分子大小进行了研究。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，该方法应用于具有（32E，29O）活动空间的Fe（II） - 孢子蛋白系统，并将其应用于A（28E，32O）活动空间中Cu2O2的异构化。
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 CASSCF wave functions obtained from selected configuration interaction, although the approach is applicable to a larger class of wave functions, including those from variational Monte Carlo (VMC). 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 in a (28e, 32o) active space.
