Accurate description of potential energy curves driven by nonbonded interactions remains a great challenge for pure density functional approximations(DFAs).It is because the Rdecay behavior of dispersion cannot be intrinsically captured by the(semi)-local ingredients and the exact-exchange used in the popular hybrid DFAs.Overemphasizing the accuracy on the equilibrium region for the functional construction would likely deteriorate the overall performance on the other regions of potential energy surfaces.In consequence,the empirical dispersion correction becomes the standard component in DFAs to treat the non-bonded interactions.In this Letter,we demonstrate that without the use of empirical dispersion correction,doubly hybrid approximations,in particular two recently proposed rev XYG3 and XYG7 functionals,hold the promise to have a balanced description of non-bonded interactions on the whole potential energy curves for several prototypes ofπ-π,CH/π,and SH/πinteractions.The error of rev XYG3 and XYG7 for non-bonded interactions is around 0.1 kcal/mol,and their potential energy curves almost coincide with the accurate CCSD(T)/CBS curves.
发现一种与球原子经验色散模型SAM深度契合的杂化泛函B972,组合成高精度的色散校正密度泛函B972-PFD。采用S66、S66x8和S22标准数据集以及大气氢键团簇、Adenine-Thymine的π…π堆叠、Watson-Crick氢键复合物和甲烷结合(H_2O)_(20)水簇等体系测试了B972-PFD的性能。测试结果显示:对于S66数据集B972-PFD方法的精度与Head-Gordon研究组的三个新泛函ωB97X-V、B97M-V和ωB97M-V处于同一水平,相对于CCSD(T)/CBS金质标准,结合能的RMSD小于1 k J?mol^(-1);在其它数据集的测试中,B972-PFD方法也表现出很好的计算精度。通过研究基函数效应,我们推荐Pople的6-311++G(2d,p)作为B972-PFD方法的最优性价比基组。
