Abstract

A two-orbital two-electron diatomic model resembling LiH is used to investigate the differences between the exact Löwdin–Shull and approximate Hartree–Fock–Bogoliubov and Baerends–Buijse density matrix functionals in the medium- to long-distance dissociation region. In case of homolytic dissociation (one electron on each atom), the approximate functionals fail to generate the correct energy due to a compromise between the Hartree–Fock component (which favors partial charge transfer) and the strong correlation component (which hampers charge transfer). The exact functional is able to generate the physically correct answer by enforcing the equi-charge distribution of the bonding and antibonding orbitals. Besides, the approximate functionals also have issues in correctly describing heterolytic dissociation (two electrons on one atom) due to the strong correlation component hampering charge transfer. In this work, we propose a new scheme in which the homolytic dissociation problem for approximate functionals is avoided by adding a Lagrange multiplier that enforces equi-charge distribution of the bonding and antibonding orbitals. The symmetry-based nature of the findings implies that they are most likely transferable to other cases in which one uses an approximate one-particle method in conjunction with a symmetrical particle-hole correction factor.

Graphical abstract

中文翻译：

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应用于杂原子键解离的近似密度矩阵泛函

摘要

一个类似于LiH的双轨道双电子双原子模型用于研究中远距离解离区域中精确Löwdin-Shull与近似Hartree-Fock-Bogoliubov和Baerends-Buijse密度矩阵函数之间的差异。在均质解离的情况下（每个原子上有一个电子），由于Hartree-Fock分量（有利于部分电荷转移）和强相关性分量（阻碍电荷转移）之间的折衷，近似功能无法生成正确的能量。精确的功能能够通过加强键合和反键合轨道的等电荷分布来产生物理上正确的答案。除了，由于强大的相关成分会阻碍电荷转移，因此近似的官能团在正确描述杂化解离（一个原子上有两个电子）方面也存在问题。在这项工作中，我们提出了一个新的方案，其中通过添加一个Lagrange乘法器来避免近似功能的均质解离问题，该Lagrange乘法器强制执行键和反键轨道的等电荷分布。研究结果基于对称性的性质意味着它们最有可能转移到其他情况下，在这种情况下，将近似单粒子方法与对称粒子-孔校正因子结合使用。我们提出了一种新方案，其中通过添加拉格朗日乘子来避免近似官能团的均质解离问题，该拉格朗日乘子强制执行键合和反键合轨道的等电荷分布。研究结果基于对称性的性质意味着它们最有可能转移到其他情况下，在这种情况下，将近似单粒子方法与对称粒子-孔校正因子结合使用。我们提出了一种新方案，其中通过添加拉格朗日乘子来避免近似官能团的均质解离问题，该拉格朗日乘子强制执行键合和反键合轨道的等电荷分布。研究结果基于对称性的性质意味着它们最有可能转移到其他情况下，在这种情况下，将近似单粒子方法与对称粒子-孔校正因子结合使用。

图形概要