title: Approaching the Hartree-Fock Limit through the Complementary Auxiliary Basis Set Singles Correction and Auxiliary Basis Sets.
abstract: Auxiliary basis sets for use in the resolution of the identity (RI) approximation in explicitly correlated methods are presented for the elements H-Ar. These extend the cc-pVnZ-F12/OptRI (n = D-Q) auxiliary basis sets of Peterson and co-workers by the addition of a small number of s- and p-functions, optimized so as to yield the greatest complementary auxiliary basis set (CABS) singles correction to the Hartree-Fock energy. The new sets, denoted OptRI+, also lead to a reduction in errors due to the RI approximation and hence an improvement in correlation energies. The atomization energies and heats of formation for a test set of small molecules, and spectroscopic constants for 27 diatomics, calculated at the CCSD(T)-F12b level, are shown to have improved error distributions for the new auxiliary basis sets with negligible additional effort. The OptRI+ sets retain all of the desirable properties of the original OptRI, including the production of smooth potential energy surfaces, while maintaining a compact nature.
authors.affiliation: Department of Chemistry, University of Sheffield , Sheffield S3 7HF, U.K.
authors.forename: Robert A
authors.initials: RA
authors.lastname: Shaw
authors.affiliation: Department of Chemistry, University of Sheffield , Sheffield S3 7HF, U.K.
authors.forename: J Grant
authors.identifier: http://orcid.org/0000-0002-6457-5837
authors.initials: JG
authors.lastname: Hill