## Abstract

One-electron basis sets for F12 explicitly-correlated molecular electronic-structure methods are assessed by analysing the accuracy of Hartree-Fock energies and valence-only second-order correlation energies of a test set of 106 small molecules containing the atoms H, C, N, O and F. For these molecules, near Hartree-Fock-limit energies and benchmark second-order correlation energies (accurate to within 99.95% of the basis-set limit) are provided. Absolute energies are analysed as well as the Hartree-Fock and second-order correlation contributions to the atomisation energies of the molecules. Standard basis sets such as the Karlsruhe def2-TZVPP and def2-QZVPP sets and the augmented correlation-consistent polarised valence X-tuple zeta (aug-cc-p VXZ, X = D, T, Q, 5) sets are compared with the specialised cc-pVXZ-F12 (X D, T, Q) sets that were recently optimised by Peterson and co-workers [J. Chem. Phys. 128, 084102 (2008)] for use in F12 theory. The results obtained from F12 explicitly-correlated molecular electronic-structure calculations are compared with those that are obtained by standard electronic-structure calculations followed by basis-set extrapolation based on the X (3) convergence behaviour of the aug-cc-pVXZ basis sets. The most important conclusions are that the cc-pVXZ-F12 sets are the preferred basis sets for F12 theory and that the X(-3) extrapolation from the aug-cc-pVQZ and aug-cc-pV5Z is slightly more accurate than F12 theory in the cc-pVTZ-F12 basis but less accurate than F12 theory in the cc-pVQZ-F12 basis.

Original language | English |
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Pages (from-to) | 963-975 |

Number of pages | 13 |

Journal | Molecular Physics |

Volume | 107 |

Issue number | 8-12 |

DOIs | |

Publication status | Published - 2009 |

## Keywords

- basis sets
- explicitly-correlated wave functions
- F12 methods
- atomisation energies
- 2ND-ORDER PERTURBATION-THEORY
- COUPLED-CLUSTER METHODS
- AUXILIARY BASIS-SETS
- ZETA BASIS-SETS
- GAUSSIAN-BASIS SETS
- PI-PI INTERACTIONS
- CORRELATION ENERGIES
- WAVE-FUNCTIONS
- WATER DIMER
- ACCURACY