Giarrusso Sara, Neugarten Roeland, Baerends Evert Jan, Giesbertz Klaas J H
Department of Chemistry and Biochemistry, University of California Merced, 5200 North Lake Road, Merced, California 95343, United States.
Department of Theoretical Chemistry and Amsterdam Center for Multiscale Modeling, FEW, Vrije Universiteit, De Boelelaan 1083, 1081HV Amsterdam, The Netherlands.
J Chem Theory Comput. 2022 Aug 9;18(8):4762-4773. doi: 10.1021/acs.jctc.2c00332. Epub 2022 Jul 27.
We consider a prototypical 1D model Hamiltonian for a stretched heteronuclear molecule and construct individual components of the corresponding KS potential, namely, the kinetic, the - 1, and the conditional potentials. These components show very special features, such as peaks and steps, in regions where the density is drastically low. Some of these features are quite well-known, whereas others, such as a secondary peak in the kinetic potential or a second bump in the conditional potential, are less or not known at all. We discuss these features building on the analytical model treated in Giarrusso et al. 2018, 14, 4151. In particular, we provide an explanation for the underlying mechanism which determines the appearance of both peaks in the kinetic potential and elucidate why these peaks delineate the region over which the plateau structure, due to the - 1 potential, stretches. We assess the validity of the Heitler-London at large but finite internuclear distance, showing that, if optimal orbitals are used, this model is an excellent approximation to the exact wave function. Notably, we find that the second natural orbital presents an extra node very far out on the side of the more electronegative atom.
我们考虑一个用于拉伸异核分子的典型一维模型哈密顿量，并构建相应KS势的各个分量，即动能势、 -1势和条件势。这些分量在密度极低的区域表现出非常特殊的特征，如峰值和台阶。其中一些特征是广为人知的，而其他一些特征，如动能势中的次级峰或条件势中的第二个凸起，则鲜为人知或完全不为人知。我们基于Giarrusso等人在2018年第14卷第4151页中处理的分析模型来讨论这些特征。特别是，我们对决定动能势中两个峰值出现的潜在机制提供了解释，并阐明了为什么这些峰值划定了由于 -1势导致的平台结构所延伸的区域。我们评估了在大但有限的核间距下Heitler-London模型的有效性，结果表明，如果使用最优轨道，该模型是精确波函数的一个极好近似。值得注意的是，我们发现第二个自然轨道在电负性更强的原子一侧非常远的地方出现了一个额外的节点。
