Department of Materials and Interfaces, Weizmann Institute of Science, Rehovoth 76100, Israel.
J Chem Phys. 2011 Oct 28;135(16):164706. doi: 10.1063/1.3655357.
Hybrid functionals often exhibit a marked improvement over semi-local functionals in the description of the electronic structure of organic materials. Because short-range hybrid functionals, notably the Heyd-Scuseria-Ernzerhof (HSE) functional, can also describe the electronic structure of metals reasonably well, it is interesting to examine to which extent they can correctly describe the electronic structure at metal-organic interfaces. Here, we address this question by comparing HSE calculations with many-body perturbation theory calculations in the GW approximation, or with experimental photoemission data, for two prototypical systems: benzene on graphite and benzene diamine on gold. For both cases, we find that while HSE yields results that are somewhat closer to experiment than those of semi-local functionals, the HSE prediction is still lacking quantitatively by ∼1 eV. We show that this quantitative failure arises because HSE does not correctly capture the fundamental gap of the organic or its renormalization by the metal. These discrepancies are traced back to missing long-range exchange and correlation components, an explanation which applies to any conventional or short-range hybrid functional.
杂化泛函在描述有机材料的电子结构方面通常优于半局域泛函。由于短程杂化泛函（特别是 Heyday-Scuseria-Ernzerhof [HSE] 泛函）也可以合理地描述金属的电子结构，因此研究它们在多大程度上可以正确描述金属-有机界面的电子结构是很有趣的。在这里，我们通过将 HSE 计算与 GW 近似的多体微扰理论计算或实验光电子能谱数据进行比较，来回答这个问题，针对两个典型的体系：苯在石墨上和苯二胺在金上。对于这两种情况，我们发现，尽管 HSE 的结果比半局域泛函更接近实验，但 HSE 的预测仍然缺乏约 1 eV 的定量准确性。我们表明，这种定量失效是由于 HSE 不能正确捕捉有机材料的基本间隙或其被金属的重整化。这些差异可以追溯到缺少长程交换和相关分量，这一解释适用于任何常规或短程杂化泛函。
