论文标题
PCCD量耦合群集波函数的轨道纠缠和相关性
Orbital entanglement and correlation from pCCD-tailored Coupled Cluster wave functions
论文作者
论文摘要
鉴于损坏的对态已适当地解释了例如后验校正，因此基于电子对状态的波函数提供了廉价且可靠的模型来描述包含强相关电子的量子多体问题。在本文中，我们分析了电子对方法在预测基于轨道的相关光谱中的性能。我们专注于（轨道优化的）成对耦合群集双打（PCCD）ANSATZ，并具有线性化的耦合群集（LCC）校正。具体而言，我们仔细检查了如何通过PCCD型CC波函数确定基于轨道的纠缠和相关措施。 Furthermore, we employ the single-orbital entropy, the orbital-pair mutual information, and the eigenvalue spectra of the two-orbital reduced density matrices to benchmark the performance of the LCC correction for the one-dimensional Hubbard model with periodic boundary condition as well as the N$_2$ and F$_2$ molecules against DMRG reference calculations.我们的研究表明，PCCD-LCC准确地重现了弱相关极限和接近其平衡结构的分子中的轨道对相关模式。因此，我们可以得出结论，PCCD-LCC可以预测该制度中可靠的波浪功能。在强相关极限和拉伸键的分子中，LCC校正通常高估了轨道对的相关性。
Wave functions based on electron-pair states provide inexpensive and reliable models to describe quantum many-body problems containing strongly-correlated electrons, given that broken-pair states have been appropriately accounted for by, for instance, a posteriori corrections. In this article, we analyse the performance of electron-pair methods in predicting orbital-based correlation spectra. We focus on the (orbital-optimized) pair-coupled cluster Doubles (pCCD) ansatz with a linearized coupled-cluster (LCC) correction. Specifically, we scrutinize how orbital-based entanglement and correlation measures can be determined from a pCCD-tailored CC wave function. Furthermore, we employ the single-orbital entropy, the orbital-pair mutual information, and the eigenvalue spectra of the two-orbital reduced density matrices to benchmark the performance of the LCC correction for the one-dimensional Hubbard model with periodic boundary condition as well as the N$_2$ and F$_2$ molecules against DMRG reference calculations. Our study indicates that pCCD-LCC accurately reproduces the orbital-pair correlation patterns in the weak-correlation limit and for molecules close to their equilibrium structure. Hence, we can conclude that pCCD-LCC predicts reliable wave functions in this regime. In the strong-correlation limit and for molecules with stretched bonds, the LCC correction, generally, overestimates orbital-pair correlations.
