Charge-shift bonds have been hypothesized as a third type of chemical bonds in addition to covalent and ionic bonds. They have first been described with valence bond theory where they are identified by the resonance energy resulting from ionic contributions. While other indicators have been described, a clear real space fingerprint for charge-shift bonding is still lacking. Probability density analysis has been developed as a real space method, allowing chemical bonding to be identified from the many-electron probability density |Ψ|² where the wave function Ψ can be obtained from any quantum chemical method. Recently, barriers of a probability potential, which depends on this density, have proven to be good measures for delocalization and covalent bonding. In this work, we employ many examples to demonstrate that a well-suited measure for charge-shift bonding can be defined within the framework of probability density analysis. This measure correlates well with the charge-shift resonance energy from valence bond theory and thus strongly supports the charge-shift bonding concept. It is, unlike the charge-shift resonance energy, not dependent on a reference state. Moreover, it is independent of the polarity of the bond, suggesting to characterize bonds in molecules by both their polarity and their charge-shift character.

中文翻译：

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通过概率密度分析确定电荷转移键合的真实空间测量

电荷转移键被假设为除了共价键和离子键之外的第三种化学键。它们首先用价键理论进行描述，通过离子贡献产生的共振能量来识别它们。尽管已经描述了其他指标，但仍然缺乏电荷转移键合的清晰的真实空间指纹。概率密度分析已发展为一种实空间方法，可以从多电子概率密度中识别化学键 | Ψ | ²其中波函数Ψ可以通过任何量子化学方法获得。最近，取决于该密度的概率势势垒已被证明是离域和共价键合的良好措施。在这项工作中，我们采用了许多例子来证明可以在概率密度分析的框架内定义一种非常合适的电荷转移键合测量方法。该测量与价键理论中的电荷转移共振能量密切相关，因此有力地支持了电荷转移键合概念。与电荷转移共振能量不同，它不依赖于参考状态。此外，它与键的极性无关，这表明可以通过极性和电荷转移特性来表征分子中的键。