Dispersion corrections# 色散修正 #

A well-know weakness of conventional density functional theory (and Hartee-Fock) is the lacking description of long-range correlation effects. These include London dispersion, the attractive component of the van-der-Waals interaction. Nevertheless, there are several well-established dispersion-corrections available to largely correct for this shortcoming. Within ORCA various options are available that include Grimme's D3 [Goerigk2011] and the more recent D4 [Grimme2017] corrections as well as the non-local variant of VV10 (NL, [Grimme2011b]) are available.
众所周知，传统密度泛函理论（以及 Hartree-Fock 方法）的一个显著弱点在于其对长程相关效应描述的缺失，这包括伦敦色散力和范德华相互作用的吸引部分。尽管如此，已有多种成熟的色散校正方法可大幅弥补这一缺陷。在 ORCA 软件中，提供了包括 Grimme 的 D3 [Goerigk2011] 和更新的 D4 [Grimme2017] 校正，以及非局域变体 VV10（NL, [Grimme2011b]）等多种选项。

Most commonly, these corrections are applied post-SCF as a correction to the obtained energy. These corrections can easily envoked by the respective simple keywords:
通常情况下，这些修正是在自洽场（SCF）计算之后应用于所得能量的校正。通过相应的简单关键词即可轻松调用这些修正：

!B3LYP D4 DEF2-TZVP

or 或

!B3LYP NL DEF2-TZVP

For NL, a self-consistent treatment is also available that can be envoked by:
对于 NL，也存在一种自洽的处理方法，可通过以下方式调用：

!B3LYP SCNL DEF2-TZVP

As the lack of London dispersion is a very systematic shortcoming of conventional DFT and Hartree-Fock, we generally recommend to use such corrections in any optimization or energy calculation with such methods.
由于缺乏伦敦色散是传统 DFT 和 Hartree-Fock 方法的一个非常系统的缺陷，我们通常建议在任何使用这些方法的优化或能量计算中采用此类修正。

Note 注释

As these corrections are of semi-empirical nature, matching parameters must be available for the functional of choice. If these are not available per default, you can provide or adjust them via the ORCA input as described in the ORCA manual.
由于这些修正具有半经验性质，必须为所选泛函提供匹配参数。如果这些参数默认不可用，您可以通过 ORCA 输入文件提供或调整它们，具体操作详见 ORCA 手册。

Example: the benzene dimer#
示例：苯二聚体 #

Let us test the impact of London dispersion on the geometry of the benzene dimer. To do so, we optimize the geometry at the B3LYP/def2-TZVP level once without correction:
让我们测试伦敦色散对苯二聚体几何结构的影响。为此，我们在 B3LYP/def2-TZVP 水平上进行一次几何优化，不加任何修正：

!B3LYP DEF2-TZVP OPT
* XYZFILE 0 1 benzene-dimer.xyz

and once with activated D4 dispersion correction:
并使用激活的 D4 色散校正进行一次：

!B3LYP D4 DEF2-TZVP OPT
* XYZFILE 0 1 benzene-dimer.xyz

Finally, we compare the structures to a reference geometry obtained at the correlated CCSD(T)/cc-pVTZ level ([Xantheas2022]) that intrinsically covers dispersion effects.
最后，我们将这些结构与在相关 CCSD(T)/cc-pVTZ 水平上获得的参考几何进行比较（[Xantheas2022]），该几何本身涵盖了色散效应。

We clearly see, that only the dispersion corrected calculation gives reasonable agreement with the high-level method. This underlines the high importance of dispersion corrections even for such small structures.As these dispersion corrections are coming at virtually no relevant additional cost, we strongly recommend to always use a dispersion correction.
我们清楚地看到，只有经过色散校正的计算结果才与高级别方法合理一致。这突显了即使在如此小的结构中，色散校正也具有极高的重要性。由于这些色散校正几乎不会带来额外的成本，我们强烈建议始终使用色散校正。

Dispersion corrections# 色散修正 #

Example: the benzene dimer#示例：苯二聚体 #

Structures# 结构

Example: the benzene dimer#
示例：苯二聚体 #