## Abstract

Explicitly correlated coupled-cluster theory has developed into a valuable computational tool for the calculation of electronic energies close to the limit of a complete basis set of atomic orbitals. In particular at the level of coupled-cluster theory with single and double excitations (CCSD), the space of double excitations is quickly extended towards a complete basis when Slater-type geminals are added to the wave function expansion. The purpose of the present article is to demonstrate the accuracy and efficiency that can be obtained in computational thermochemistry by a CCSD model that uses such Slater-type geminals. This model is denoted as CCSD(F12), where the acronym F12 highlights the fact that the Slater-type geminals are functions f(r (12)) of the interelectronic distances r (12) in the system. The performance of explicitly correlated CCSD(F12) coupled-cluster theory is demonstrated by computing the atomization energies of 73 molecules (containing H, C, N, O, and F) with an estimated root-mean-square deviation from the values compiled in the Active Thermochemical Tables of sigma = 0.10 kJ/mol per valence electron. To reach this accuracy, not only the frozen-core CCSD basis-set limit but also high-order excitations (connected triple and quadruple excitations), core-valence correlation effects, anharmonic vibrational zero-point energies, and scalar and spin-orbit relativistic effects must be taken into account.

Original language | English |
---|---|

Pages (from-to) | 289-304 |

Number of pages | 16 |

Journal | Theoretical Chemistry Accounts |

Volume | 126 |

Issue number | 5-6 |

DOIs | |

Publication status | Published - Aug 2010 |

## Keywords

- Thermochemistry
- Atomization energy
- Coupled-cluster theory
- Explicitly correlated theory
- Basis-set extrapolation
- COMPLETE BASIS-SET
- GAUSSIAN-BASIS SETS
- MOLECULAR ELECTRONIC-STRUCTURE
- CONSISTENT COMPOSITE APPROACH
- AB-INITIO THERMOCHEMISTRY
- PERTURBATION-THEORY CALCULATIONS
- MULTI-COEFFICIENT CORRELATION
- DENSITY-FUNCTIONAL METHODS
- AUXILIARY BASIS-SETS
- INFINITE BASIS-SET