Ivanov Aleksei V, Ghosh Tushar K, Jónsson Elvar Ö, Jónsson Hannes
Science Institute and Faculty of Physical Sciences, University of Iceland VR-III, 107 Reykjavík, Reykjavik, Iceland.
St. Petersburg State University, St. Petersburg 199034, Russia.
J Phys Chem Lett. 2021 May 6;12(17):4240-4246. doi: 10.1021/acs.jpclett.1c00364. Epub 2021 Apr 26.
Qualitatively incorrect results are obtained for the Mn dimer in density functional theory calculations using the generalized gradient approximation (GGA), and similar results are obtained from local density and meta-GGA functionals. The coupling is predicted to be ferromagnetic rather than antiferromagnetic, and the bond between the atoms is predicted to be an order of magnitude too strong and approximately an Ångstrøm too short. Explicit, self-interaction correction (SIC) applied to a commonly used GGA energy functional, however, provides close agreement with both experimental data and high-level, multireference wave function calculations. These results show that the failure is not due to a strong correlation but rather the single electron self-interaction that is necessarily introduced in estimates of the classical Coulomb and exchange-correlation energy when only the total electron density is used as the input. The corrected functional depends explicitly on the orbital densities and can, therefore, avoid the introduction of a self-Coulomb interaction. The error arises because of an overstabilization of bonding d-states in the minority spin channel resulting from an overestimate of the d-electron self-interaction in the semilocal exchange-correlation functionals. Since the computational effort in the SIC calculations scales with the system size in the same way as for regular semilocal functional calculations, this approach provides a way to calculate properties of Mn nanoclusters as well as biomolecules and extended solids, where Mn dimers and larger cluster are present, while multireference wave function calculations can only be applied to small systems.
在使用广义梯度近似（GGA）的密度泛函理论计算中，对于锰二聚体得到了定性错误的结果，并且从局域密度和元GGA泛函也得到了类似的结果。耦合被预测为铁磁性而非反铁磁性，并且原子之间的键被预测要强一个数量级且短约一个埃。然而，将显式自相互作用校正（SIC）应用于常用的GGA能量泛函时，与实验数据以及高水平的多参考波函数计算都能得到密切的一致性。这些结果表明，失败并非由于强关联，而是由于仅使用总电子密度作为输入来估计经典库仑能和交换关联能时必然引入的单电子自相互作用。校正后的泛函明确依赖于轨道密度，因此可以避免引入自库仑相互作用。误差源于半局域交换关联泛函中d电子自相互作用的高估导致少数自旋通道中键合d态的过度稳定。由于SIC计算中的计算量与系统大小的比例关系与常规半局域泛函计算相同，这种方法提供了一种计算存在锰二聚体和更大团簇的锰纳米团簇以及生物分子和扩展固体性质的方法，而多参考波函数计算只能应用于小系统。
