Open-shell explicitly correlated F12 methods

David P. Tew, Wim Klopper*

*Corresponding author for this work

Research output: Contribution to journalArticle (Academic Journal)peer-review

37 Citations (Scopus)

Abstract

In calculations on open-shell systems, spin-flipped geminals must be used in explicitly correlated F12 methods with spin-unrestricted or restricted open-shell Hartree-Fock reference wave functions. We suggest the use of the sp ansatz of Bokhan et al. [J. Chem. Phys. 131, 084105 (2009)] for calculations with fixed F12 amplitudes, but to use a novel contracted geminal approach if the F12 amplitudes are to be optimised. This new approach is denoted MP2-F12-o (CCSD(F12)-o). The performance of the new approach is assessed by calculating the atomisation energies of a test set comprising 106 molecules containing the atoms H, C, N, O and F, and by calculating the ionisation energies and electron affinities of the atoms C, N, O and F.

Original languageEnglish
Pages (from-to)315-325
Number of pages11
JournalMolecular Physics
Volume108
Issue number3-4
DOIs
Publication statusPublished - 2010

Keywords

  • open-shell systems
  • electron correlation
  • geminals
  • correlation cusp
  • AUXILIARY BASIS-SETS
  • ZETA BASIS-SETS
  • 2ND-ORDER PERTURBATION-THEORY
  • CLUSTER CORRELATION ENERGIES
  • ELECTRONIC-STRUCTURE THEORY
  • CORRELATION CUSP
  • FORMULATION

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