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Modified electron gas approach to estimate correlation energy: gradient expansion correction and spin-parallel correlation

机译：估计相关能量的改进电子气方法：梯度膨胀校正和自旋平行相关

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摘要

In refs. [1, 2], we proposed a modified electron gas approach (MEGA), with self-interaction correction (SIC) and spin-parallel correlation correction (SPCC) to the local density approximation (LDA), to estimate correlation energies of many electron systems. It was found that MEGA gives correlation energies for many neutral atoms and molecules with quite low relative errors, 5% and 10% respectively. However, for the highly ionized atoms MEGA cannot give good results. This is due to the different gradient effects of such two cases. Based on the assumption that the Hartree-Fock (HF) limit includes all spin-parallel correlation, MEGA thus overcorrects the spin-parallel error of- LDA; on the other hand, as a zero-order gradient expansion approximation, LDA has not considered the density inhomogeneity of real system and hence overestimates the correlation energy. For neutral atoms and molecules, the positive and negative effects can be canceled out. But in the case of highly ionized atoms, the cancel isimpossible owing to the fact that the gradient effect becomes pronounced there.
机译：在裁判。 [1，2]，我们提出了一种改进的电子气法（MEGA），它具有自交互校正（SIC）和自旋平行相关校正（SPCC）到局部密度近似（LDA），以估计许多电子的相关能系统。结果发现，MEGA可以为许多中性原子和相对误差非常低的分子（分别为5％和10％）提供相关能。但是，对于高度离子化的原子，MEGA无法提供良好的结果。这是由于这两种情况的梯度效果不同。基于Hartree-Fock（HF）极限包括所有自旋平行相关性的假设，MEGA因此过度校正了LDA的自旋平行误差。另一方面，作为零阶梯度展开近似，LDA并未考虑实际系统的密度不均匀性，因此高估了相关能量。对于中性原子和分子，可以消除正负效应。但是在高度离子化的原子的情况下，由于梯度效应在那里变得明显，因此消除是不可能的。

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