Řezáč Jan, Dubecký Matúš, Jurečka Petr, Hobza Pavel
Institute of Organic Chemistry and Biochemistry, Academy of Sciences of the Czech Republic, 166 10 Prague, Czech Republic.
Phys Chem Chem Phys. 2015 Jul 15;17(29):19268-77. doi: 10.1039/c5cp03151f.
The A24 data set (Řezáč and Hobza, J. Chem. Theory Comput. 2013, 9, 2151-2155) is a set of noncovalent complexes large enough to showcase various types of interactions yet small enough to make highly accurate calculations possible. It is intended for the testing of accurate computational methods which are then used as a benchmark in larger model systems. In this work, we improve the best estimate of the interaction energies in the set by updating their CCSD(T)/CBS and CCSDT(Q) components with calculations in larger basis sets. The data set is then used to test a large number of composite CCSD(T) approaches. Special attention is paid to the use of the explicitly correlated MP2-F12 method in these composite calculations. It is shown that an accuracy of 1-2% can be achieved with setups applicable to larger molecules. The effect of frozen natural orbital approximation on the accuracy of composite CCSD(T)/CBS calculations is also quantified. In four trivially saturated complexes where CCSDT(Q)/CBS data are now available, the convergence of the many-body correlation effects is assessed by fixed-node diffusion Monte Carlo (FN-DMC) calculations. A good agreement is achieved between FN-DMC and high-level coupled-cluster which represents an important cross-check of both approaches.
A24数据集（Řezáč和Hobza，《化学理论与计算杂志》，2013年，第9卷，2151 - 2155页）是一组非共价复合物，其规模大到足以展示各种类型的相互作用，同时又小到足以进行高精度计算。它旨在用于测试精确的计算方法，这些方法随后可作为更大模型系统中的基准。在这项工作中，我们通过在更大的基组中进行计算来更新CCSD(T)/CBS和CCSDT(Q)分量，从而改进了该数据集中相互作用能的最佳估计值。然后，该数据集被用于测试大量的复合CCSD(T)方法。在这些复合计算中，特别关注了显式相关MP2-F12方法的使用。结果表明，对于适用于更大分子的设置，可以实现1 - 2%的精度。还对冻结自然轨道近似对复合CCSD(T)/CBS计算精度的影响进行了量化。在现在已有CCSDT(Q)/CBS数据的四个简单饱和复合物中，通过固定节点扩散蒙特卡罗（FN-DMC）计算评估了多体相关效应的收敛性。FN-DMC与高水平耦合簇之间取得了良好的一致性，这对两种方法来说都是重要的交叉检验。
