Tozer David J, De Proft Frank
Department of Chemistry, University of Durham, South Road, Durham DH1 3LE, United Kingdom.
J Chem Phys. 2007 Jul 21;127(3):034108. doi: 10.1063/1.2751158.
Two approaches are investigated for modeling electron densities of temporary anions in density functional theory (DFT). Both rely on an artificial binding of the excess electron, in one case by a compact basis set and in the other by a potential wall. The key feature of the calculations is that the degree of binding is controlled in both cases by knowledge of the negative electron affinity of the corresponding neutral, approximated in terms of DFT local functional frontier orbital eigenvalues and vertical ionization potential, A=-(epsilon(LUMO)+epsilon(HOMO))-I. To illustrate the two approaches, Fukui functions for nucleophilic attack are determined in four molecules with increasingly negative electron affinities. They yield very similar results, which are notably different to those determined without artificial electron binding. The use of a potential wall has the attractive feature that large, diffuse basis sets can be used, avoiding the need for a compact basis, tailored to a particular molecule.
在密度泛函理论（DFT）中，研究了两种用于模拟临时阴离子电子密度的方法。这两种方法都依赖于对多余电子的人工束缚，一种情况是通过紧束缚基组，另一种情况是通过势垒。计算的关键特征是，在这两种情况下，束缚程度都由相应中性物质的负电子亲合势来控制，该势通过DFT局域泛函前沿轨道本征值和垂直电离势进行近似，即A = -（ε（LUMO）+ε（HOMO））-I。为了说明这两种方法，在四个具有越来越负的电子亲合势的分子中确定了亲核进攻的福井函数。它们产生了非常相似的结果，这与没有人工电子束缚时确定的结果明显不同。使用势垒具有吸引人的特点，即可以使用大的、弥散的基组，避免了为特定分子量身定制紧束缚基组的需要。
