Laboratorium für Physikalische Chemie , ETH Zürich , Vladimir-Prelog-Weg 2 , 8093 Zürich , Switzerland.
J Chem Theory Comput. 2018 Oct 9;14(10):5169-5179. doi: 10.1021/acs.jctc.8b00601. Epub 2018 Sep 21.
Many modern semiempirical molecular orbital models are built on the neglect of diatomic differential overlap (NDDO) approximation. An in-depth understanding of this approximation is therefore indispensable to rationalize the success of these semiempirical molecular orbital models and to develop further improvements on them. The NDDO approximation provides a recipe to approximate electron-electron repulsion integrals (ERIs) in a symmetrically orthogonalized basis based on a far smaller number of ERIs in a locally orthogonalized basis. We first analyze the NDDO approximation by comparing ERIs in both bases for a selection of molecules and for a selection of basis sets. We find that the errors in Hartree-Fock and second-order Møller-Plesset perturbation theory energies grow roughly linearly with the number of basis functions. We then examine different approaches to correct for the errors caused by the NDDO approximation and propose a strategy to directly correct for them in the two-electron matrices that enter the Fock operator.
许多现代半经验分子轨道模型都是基于忽略双原子微分重叠（NDDO）近似的。因此，深入了解这种近似对于合理化这些半经验分子轨道模型的成功并进一步改进它们是必不可少的。NDDO 近似提供了一种根据局部正交化基中的较小数量的电子-电子排斥积分（ERI）来近似对称正交化基中的 ERI 的方法。我们首先通过比较分子和基组的选择中的两个基中的 ERI 来分析 NDDO 近似。我们发现 Hartree-Fock 和二阶 Møller-Plesset 微扰理论能量中的误差大致与基函数的数量呈线性关系。然后，我们研究了不同的方法来纠正 NDDO 近似引起的误差，并提出了一种在进入 Fock 算子的双电子矩阵中直接纠正它们的策略。
