Functional extrapolations to tame unbound anions in density-functional theory calculations.
Functional extrapolations to tame unbound anions in density-functional theory calculations.
复制标题
在密度泛函理论计算中驯服未结合阴离子的函数外推。
DOI：
--
复制
发表时间：
2019
影响因子：
5.5
通讯作者：
O. Andreussi
中科院分区：
文献类型：
--
作者：
F. Nattino;C. Dupont;N. Marzari;O. Andreussi
众所周知，由于自相互作用误差较大，标准的密度泛函理论 (DFT) 计算无法描述阴离子。这个问题可以通过使用尺寸减小的局域基组来避免，这样就不会为额外的电子离域留下任何变分灵活性。另外，最近报道了一种利用 DFT 评估在 Hartree-Fock (HF) 水平上优化的电子密度总能量的方法，表明无自相互作用的 HF 密度能够改进对附加电子的描述，返回与实验非常一致的亲和力。尽管如此，当高频密度太不准确时，这种方法可能会失败。在这里，提出了一种替代方法，其中使用嵌入环境来稳定结合配置中的阴离子。与 HF 情况类似，当在这些校正密度上计算 DFT 水平的总能量时，可以恢复与实验非常一致的电子亲和势。可以通过将结果外推到消失嵌入的极限来评估和消除环境的影响。除了嵌入势域的定义之外，该方法不受参数限制，并且可以轻松应用于具有离域基组的 DFT 计算，例如平面波，对于这种情况，替代方法要么不可行，要么计算要求更高。因此，所提出的外推策略也可以应用于扩展系统，正如凝聚态物理和材料科学中经常研究的那样，并且我们说明了如何利用嵌入环境来确定吸附阴离子（这里是金属表面上的氯离子）的能量，其电荷配置将被标准密度泛函错误地预测。
Standard flavors of density-functional theory (DFT) calculations are known to fail in describing anions, due to large self-interaction errors. The problem may be circumvented by using localized basis sets of reduced size, leaving no variational flexibility for the extra electron to delocalize. Alternatively, a recent approach exploiting DFT evaluations of total energies on electronic densities optimized at the Hartree-Fock (HF) level has been reported, showing that the self-interaction-free HF densities are able to lead to an improved description of the additional electron, returning affinities in close agreement with the experiments. Nonetheless, such an approach can fail when the HF densities are too inaccurate. Here, an alternative approach is presented, in which an embedding environment is used to stabilize the anion in a bound configuration. Similarly to the HF case, when computing total energies at the DFT level on these corrected densities, electron affinities in very good agreement with experiments can be recovered. The effect of the environment can be evaluated and removed by an extrapolation of the results to the limit of vanishing embedding. Apart from the definition of the domain of the embedding potential, the approach is free from parameters and it can be easily applied to DFT calculations with delocalized basis sets, e.g. plane-waves, for which alternative approaches are either not viable or more computationally demanding. The proposed extrapolation strategy can be thus applied also to extended systems, as often studied in condensed-matter physics and materials science, and we illustrate how the embedding environment can be exploited to determine the energy of an adsorbing anion - here a chloride ion on a metal surface - whose charge configuration would be incorrectly predicted by standard density functionals.