论文标题
高阶电子相关效应在模型系统中的非价相关性阴离子的作用
The Role of High-Order Electron Correlation Effects in a Model System for Non-valence Correlation-bound Anions
论文作者
论文摘要
使用扩散的蒙特卡洛（DMC），辅助场量子蒙特卡洛（AFQMC）和运动方程耦合群集（EOM-CC）方法用于计算模型的非价值阴离子状态的电子结合能（EBE）（H $ _2 $ O）$ _2 $ o）$ _ 4 $ _ 4 $ _ 4 $ _ 4 $ _ 4 $ cluster。考虑了两个几何形状，一个阴离子是未结合的，另一个是在Hartree-fock（HF）近似中结合的。证明DMC的计算可以从使用HF试验波函数的使用中恢复，该HF试验波函数已崩溃到离散的连续溶液上，尽管当使用试验波函数为阴离子使用试验波函数时获得了更大的电子结合能，该阴离子提供了对电荷分布的更现实描述，因此，鼻表面的电荷分布。对于簇具有非价相关性阴离子的几何形状，将三元组包含在EOM-CC方法中，并且在基础集中包含补充弥漫性D函数都很重要。具有适当试验波函数的DMC计算使EBE值与我们的最佳估计EOM-CC结果非常吻合。使用相同基集时，使用具有现实电子密度的阴离子的AFQMC具有现实电子密度的阴离子函数几乎与EOM-CC结果相同。对于在HF近似中结合阴离子的几何形状，在EOM-CC计算中包含三重激发的重要性要重要得多。最佳估计值EOM-CC EBE值与具有适当试验波函数的DMC计算结果非常吻合。
The diffusion Monte Carlo (DMC), auxiliary field quantum Monte Carlo (AFQMC), and equation-of-motion coupled cluster (EOM-CC) methods are used to calculate the electron binding energy (EBE) of the non-valence anion state of a model (H$_2$O)$_4$ cluster. Two geometries are considered, one at which the anion is unbound and the other at which it is bound in the Hartree-Fock (HF) approximation. It is demonstrated that DMC calculations can recover from the use of a HF trial wave function that has collapsed onto a discretized continuum solution, although larger electron binding energies are obtained when using a trial wave function for the anion that provides a more realistic description of the charge distribution, and, hence, of the nodal surface. For the geometry at which the cluster has a non-valence correlation-bound anion, both the inclusion of triples in the EOM-CC method and the inclusion of supplemental diffuse d functions in the basis set are important. DMC calculations with suitable trial wave functions give EBE values in good agreement with our best estimate EOM-CC result. AFQMC using a trial wave function for the anion with a realistic electron density gives a value of the EBE nearly identical to the EOM-CC result when using the same basis set. For the geometry at which the anion is bound in the HF approximation, the inclusion of triple excitations in the EOM-CC calculations is much less important. The best estimate EOM-CC EBE value is in good agreement with the results of DMC calculations with appropriate trial wave functions.
