title: Convergence of third order correlation energy in atoms and molecules.
abstract: We have investigated the convergence of third order correlation energy within the hierarchies of correlation consistent basis sets for helium, neon, and water, and for three stationary points of hydrogen peroxide. This analysis confirms that singlet pair energies converge much slower than triplet pair energies. In addition, singlet pair energies with (aug)-cc-pVDZ and (aug)-cc-pVTZ basis sets do not follow a converging trend and energies with three basis sets larger than aug-cc-pVTZ are generally required for reliable extrapolations of third order correlation energies, making so the explicitly correlated R12 calculations preferable.
authors.affiliation: Department of Chemistry and Biochemistry, University of California, Santa Barbara, California 93106, USA. kalju@chem.ucsb.edu
authors.forename: Kalju
authors.initials: K
authors.lastname: Kahn
authors.forename: Alex A
authors.initials: AA
authors.lastname: Granovsky
authors.forename: Jozef
authors.initials: J
authors.lastname: Noga