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Keld L. Bak

Coupled-cluster singles, doubles and triples (CCSDT) calculations of atomization energies

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  • Keld L. Bak
  • Poul Jørgensen
  • Jeppe Olsen
  • T. Helgaker, Department of Chemistry, University of Cambridge, Cambridge, UK.
  • ,
  • J. Gauss, Department of Chemistry, University of Cambridge, Cambridge, UK.
Atomization energies have been calculated for CO, H2O, F-2, HF, N-2 and CH2 (the (1)A(1) state) using the coupled-duster singles, doubles and triples (CCSDT) model as well as the coupled-cluster singles and doubles model with a perturbative correction for triples [CCSD(T)]. TheCCSD(T) model provides an excellent approximation to the CCSDT model; at the cc-pV5Z basis set level, the CCSDT valence triples contribution is underestimated by 9.1% (0.8 kJ/mol) for CH, and overestimated for the remaining molecules by as little as 4.3%(1.3 kJ/mol) for F-2,and as much as 8.4% (3.0 kJ/mol) for N-2. At the CCSDT level, the agreement with experiment is not improved, suggesting that some cancellation of error occurs between the missing triples contributions at the CCSD(T) level and the contributions from the connected quadruples. (C) 2000 Elsevier Science B.V, All rights reserved.
Original languageEnglish
JournalChemical Physics Letters
Volume317
Issue1-2
Pages (from-to)116-122
Number of pages7
ISSN0009-2614
DOIs
Publication statusPublished - 2000

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