Department of Chemistry and Biochemistry , Auburn University , Auburn , Alabama 36849 , United States.
J Chem Theory Comput. 2018 Jun 12;14(6):3053-3070. doi: 10.1021/acs.jctc.8b00204. Epub 2018 May 30.
We investigate the effect of adding midbond basis functions on the performance of various conventional and explicitly correlated (F12) estimates of complete basis set limit coupled-cluster (CCSD(T)/CBS) noncovalent interaction energies. In particular, we search for an improved "silver standard" of interaction energy calculations for systems where the CCSD(T) computation is feasible in a double-ζ basis but not in a triple-ζ one. We follow a recent study ( Sirianni J. Chem. Theory Comput. 2017 , 13 , 86 ) of different CCSD(T)-F12 variants in midbondless bases over the A24 and S22 benchmark interaction energy databases, and extend Dunning's correlation-consistent basis sets with three different midbond sets. The addition of bond functions is highly beneficial for conventional CCSD(T) and most CCSD(T)-F12 variants, improving both the CCSD part and the unscaled triples contribution. However, the commonly used scaling of triples by the ratio of the MP2-F12 and MP2 correlation energies usually overshoots: as a result, the scaled triples term gets worse upon the addition of bond functions. In contrast, a milder triples scaling by the ratio of the CCSD-F12b and CCSD correlation energies ( Brauer , Phys. Chem. Chem. Phys. 2016 , 18 , 20905 ) leads to the most accurate estimates of this term as long as bond functions are included. The combination of the triples term scaled in this way with the CCSD-F12b interaction energy leads to the CCSD(Tbb)-F12b approach that provides consistent high accuracy when a (3 s3 p2 d2 f) set of midbond functions is added to the aug-cc-pVDZ atom-centered basis set. The combination of midbond functions and the composite MP2/CBS+δ(CCSD(T)) treatment is able to make up for the deficiencies in the atom-centered part of the basis set, in particular, for a partial (or even complete) lack of diffuse functions. Considering both the A24 and S22 accuracy and the computational efficiency, we propose several new "silver standard" approaches improving upon the currently established midbondless levels of theory, ranging from the most consistent CCSD(Tbb)-F12b/aug-cc-pVDZ+(3 s3 p2 d2 f) variant (with mean unsigned errors of 0.010 and 0.042 kcal/mol for the A24 and S22 databases, respectively) to the significantly cheaper MP2/CBS+δ(CCSD(T))/cc-pVDZ+(3 s3 p2 d2 f) approach (mean unsigned errors of 0.039 and 0.096 kcal/mol for A24 and S22, respectively).
我们研究了在各种常规和显式相关（F12）完全基组限制耦合簇（CCSD（T）/CBS）非共价相互作用能估计中添加中键基函数对性能的影响。特别是，我们寻找一种改进的“银标准”，用于计算那些在双ζ基中可行但在三ζ基中不可行的 CCSD（T）计算的系统的相互作用能。我们遵循最近一项关于不同 CCSD（T）-F12 变体在 A24 和 S22 基准相互作用能数据库中无键中键基中的研究（Sirianni J. Chem. Theory Comput. 2017, 13, 86），并扩展了 Dunning 的相关一致基集，使用三种不同的中键集。键函数的添加对常规 CCSD（T）和大多数 CCSD（T）-F12 变体都非常有益，这提高了 CCSD 部分和未经缩放的三重贡献。然而，通常使用 MP2-F12 和 MP2 相关能的比值来缩放三重态会过度校正：结果是，在添加键函数后，缩放的三重态项会变得更糟。相比之下，使用 CCSD-F12b 和 CCSD 相关能的比值对三重态进行适度缩放（Brauer，Phys. Chem. Chem. Phys. 2016, 18, 20905），只要包含键函数，就能得到此项最准确的估计。以这种方式缩放的三重态项与 CCSD-F12b 相互作用能相结合，得到 CCSD（Tbb）-F12b 方法，当在 aug-cc-pVDZ 原子中心基集中添加（3 s3 p2 d2 f）套中键函数时，该方法提供一致的高精度。中键函数与复合 MP2/CBS+δ（CCSD（T））处理的结合能够弥补基集原子中心部分的缺陷，特别是部分（甚至完全）缺乏弥散函数。考虑到 A24 和 S22 的准确性和计算效率，我们提出了几种新的“银标准”方法，在目前建立的无键理论水平上进行改进，范围从最一致的 CCSD（Tbb）-F12b/aug-cc-pVDZ+（3 s3 p2 d2 f）变体（对于 A24 和 S22 数据库，平均无符号误差分别为 0.010 和 0.042 kcal/mol）到明显更便宜的 MP2/CBS+δ（CCSD（T））/cc-pVDZ+（3 s3 p2 d2 f）方法（对于 A24 和 S22，平均无符号误差分别为 0.039 和 0.096 kcal/mol）。
