Chemical Research Center, Hungarian Academy of Sciences, Budapest, Hungary.
J Phys Chem A. 2011 Nov 17;115(45):12733-7. doi: 10.1021/jp2036923. Epub 2011 Jun 23.
Effective atomic orbitals (AOs) have been calculated by the method of the "fuzzy atoms" analysis by using the numerical molecular orbitals (MOs) obtained from plane-wave DFT calculation, i.e., without introducing any atom-centered functions. The results show that in the case of nonhypervalent atoms there are as many effective AOs with non-negligible occupation numbers, as many orbitals are in the classical minimal basis set of the given atom. This means that, for nonhypervalent systems, it is possible to present the MOs as sums of effective atomic orbitals that resemble very much the atomic minimal basis orbitals of the individual atoms (or their hybrids). For hypervalent atoms some additional orbitals basically of d-type are also of some importance; they are necessary to describe the back-donation to these positive atoms. It appears that the d-type orbitals play a similar role also for strongly positive carbon atoms. The method employed here is also useful to decide whether the use of polarization functions of a given type is a matter of conceptual importance or has only a numerical effect.
已通过使用源自平面波密度泛函计算的数值分子轨道（MO）的“模糊原子”分析方法计算有效原子轨道（AOs），即不引入任何原子中心函数。结果表明，在非高价原子的情况下，具有非零占据数的有效 AOs 的数量与给定原子的经典最小基函数中的轨道数量一样多。这意味着，对于非高价体系，可以将 MO 表示为有效原子轨道的和，这些轨道非常类似于各个原子（或它们的杂化）的原子最小基轨道。对于高价原子，一些基本为 d 型的附加轨道也很重要；它们是描述这些正原子的反馈的必要条件。对于带强正电荷的碳原子，d 型轨道似乎也起着类似的作用。这里采用的方法也可用于确定给定类型的极化函数的使用是概念上的重要问题还是仅具有数值影响。
