Bruneval Fabien
CEA, DEN, Service de Recherches de Métallurgie Physique, F-91191 Gif-sur-Yvette, France.
Phys Rev Lett. 2009 Oct 23;103(17):176403. doi: 10.1103/PhysRevLett.103.176403.
A stringent test for an exchange-correlation approximation in electronic structure calculations is the equality between the ionization energy of the neutral system and the affinity of the singly positively charged system. All of the commonly used approximations (local, semilocal, hybrid) for the exchange correlation within density functional theory fail badly with this test. They consequently present a localization or delocalization error, resulting in a highest occupied molecular orbital or lowest unoccupied molecular orbital gap over- or underestimation. The GW approximation appears as the best available framework to describe particle number changes. The small remaining error can be further reduced by devising a DeltaSCF-like method within the GW approximation. The proposed approach is necessary as soon as localized states are involved, e.g., in finite systems or defect states in crystals.
电子结构计算中对交换关联近似的一个严格测试是中性系统的电离能与单正电荷系统的亲和能之间的相等关系。密度泛函理论中所有常用的交换关联近似（局域、半局域、杂化）在这个测试中都表现很差。因此，它们存在局域化或离域化误差，导致最高占据分子轨道或最低未占据分子轨道能隙被高估或低估。GW近似似乎是描述粒子数变化的最佳可用框架。通过在GW近似内设计一种类似DeltaSCF的方法，可以进一步减小剩余的小误差。一旦涉及到局域态，例如在有限系统或晶体中的缺陷态中，所提出的方法就是必要的。
