Journal
JOURNAL OF CHEMICAL THEORY AND COMPUTATION
Volume 9, Issue 1, Pages 330-337Publisher
AMER CHEMICAL SOC
DOI: 10.1021/ct300842d
Keywords
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Funding
- Leverhulme Trust for a Research Fellowship
- EPSRC [EP/K000586/1]
- Institute of Organic Chemistry and Biochemistry, Academy of Sciences of the Czech Republic [RVO: 61388963]
- Czech Science Foundation [P208/12/G016]
- U.K. National Service for Computational Chemistry Software
- Engineering and Physical Sciences Research Council [EP/J003921/1, EP/K000586/1] Funding Source: researchfish
- EPSRC [EP/J003921/1] Funding Source: UKRI
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We report the performance of composite post-MP2 ab initio methods with small basis sets for description of noncovalent interactions, using the S66 data set as a benchmark. For three representative complexes, it is shown that explicitly correlated coupled cluster (CCSD-F12a) methods yield interaction energies ca. 0.1 kcal/mol from the complete basis set limit with aug-cc-pVDZ. Triple excitations are not explicitly correlated in this approach, but we show that scaling the perturbative triples via the (T*) approximation improves agreement with benchmark values. Across the entire S66 data set, this approach results in a root-mean-square error (RMSE) of 0.13 kcal/mol or 3%, with well-balanced description of all classes of complex. The basis set dependence of traditional CCSD(T) interaction energies is examined, and the small 6-31G*(0.25) basis set is found to give particularly accurate results (RMSE = 0.15 kcal/mol, or 4%). We also employ spin component scaling (SCS) of CCSD-F12a data, which gives slightly better accuracy than CCSD(T*)-F12a if contributions from same- and opposite-spin pairs are optimized for this data set (RMSE = 0.08 kcal/mol, or 2%). Interpolation of local MP2 and MP3 is also shown to accurately reproduce benchmark data with both aug-cc-pVDZ (RMSE = 0.18 kcal/mol or 5%) and 6-31G*(0.25) (RMSE = 0.13 kcal/mol or 4%).
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