title: Basis Set Dependence of Interaction Energies Computed Using Composite Post-MP2 Methods.
abstract: 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%).
authors.affiliation: School of Chemistry, Cardiff University , Park Place, Cardiff CF10 3AT, United Kingdom.
authors.forename: James A
authors.initials: JA
authors.lastname: Platts
authors.affiliation: School of Chemistry, University of Glasgow , Joseph Black Building, University Ave, Glasgow, G12 8QQ, United Kingdom.
authors.forename: J Grant
authors.initials: JG
authors.lastname: Hill
authors.affiliation: Department of Chemistry, Xavier University of Louisiana , 1 Drexel Drive, Box 22, New Orleans, Louisiana 70125, United States.
authors.forename: Kevin E
authors.initials: KE
authors.lastname: Riley
authors.affiliation: Institute of Organic Chemistry and Biochemistry, Academy of Sciences of the Czech Republic and Center for Biomolecules and Complex Molecular Systems , 166 10 Prague, Czech Republic.
authors.forename: Jan
authors.initials: J
authors.lastname: Řezáč
authors.affiliation: Institute of Organic Chemistry and Biochemistry, Academy of Sciences of the Czech Republic and Center for Biomolecules and Complex Molecular Systems , 166 10 Prague, Czech Republic.
authors.forename: Pavel
authors.initials: P
authors.lastname: Hobza