论文标题
改善了具有范德华密度功能的质子转移屏障:排斥性非本地相关的作用
Improved proton-transfer barriers with van der Waals density functionals: Role of repulsive non-local correlation
论文作者
论文摘要
有机络合物之间的质子转移(PT)是一个常见和重要的生化过程。不幸的是,使用密度功能理论(DFT)很难准确预测PT的能屏障。特别是,广义梯度近似(GGA)倾向于低估PT屏障。此外,PT通常发生在分散力有助于系统凝聚力的环境中。因此,合适的交换相关功能应准确地描述分散力和PT屏障。本文为几个密度函数的PT屏障提供了基准结果,包括范德华密度函数(VDWDF)的几种变体。基准组包括带有分子间和分子内PT的小有机分子。结果表明,用完全非本地VDW-DF相关性代替GGA相关性会增加PT屏障,从而更接近量子化学参考值。相反,包括与DFT-D3或Tkatchenko-Scheffler(TS)水平的Vydrov-Voorhis(VV)方法或分散校正的非局部相关性几乎没有对PT障碍的任何影响。混合功能还会增加和提高能量,最佳性能由一致的交换范德华密度功能VDW-DF-CX提供的混合版本提供。对于甲酸二聚体PT系统,我们分析了GGA交换和非本地相关贡献。分析表明,非本地相关内核的排斥部分在VDW-DF预测的PT能屏障中起关键作用。
Proton-transfer (PT) between organic complexes is a common and important biochemical process. Unfortunately, PT energy barriers are difficult to accurately predict using density functional theory (DFT); in particular, the generalized gradient approximation (GGA) tends to underestimate PT barriers. Moreover, PT typically occurs in environments where dispersion forces contribute to the cohesion of the system; thus, a suitable exchange-correlation functional should accurately describe both dispersion forces and PT barriers. This paper provides benchmark results for the PT barriers of several density functionals including several variants of the van der Waals density functional (vdWDF). The benchmark set comprises small organic molecules with inter- and intra-molecular PT. The results show that replacing GGA correlation with a fully non-local vdW-DF correlation increases the PT barriers, making it closer to the quantum chemical reference values. In contrast, including nonlocal correlations with the Vydrov-Voorhis (VV) method or dispersion-corrections at the DFT-D3 or the Tkatchenko-Scheffler (TS) level has barely any impact on the PT barriers. Hybrid functionals also increase and improve the energies and the best performance is provided by a hybrid version of the consistent-exchange van der Waals density functional vdW-DF-cx. For the formic acid dimer PT system, we analyzed the GGA exchange and non-local correlation contributions. The analysis shows that the repulsive part of the non-local correlation kernel plays a key role in the PT energy barriers predicted with vdW-DF.