Single-reference, size-extensive, non-iterative coupled-cluster approaches to bond breaking and biradicals

Piecuch P., Wloch M., Gour J., Kinal A.

CHEMICAL PHYSICS LETTERS, cilt.418, ss.467-474, 2006 (SCI İndekslerine Giren Dergi) identifier identifier

  • Cilt numarası: 418
  • Basım Tarihi: 2006
  • Doi Numarası: 10.1016/j.cplett.2005.10.116
  • Sayfa Sayıları: ss.467-474


We propose the non-iterative, completely renormalized (CR) coupled-cluster (CC) approaches, including the CR-CC(2,3) method which offers considerable improvements over the CCSD(T) approach without a significant increase in the computer effort. The CR-CC(2,3) method, in which the CCSD (CC singles and doubles) energy is corrected for the effect of triples, is size extensive, competitive with CCSD(T) in calculations for non-degenerate states, and as accurate as the expensive CC approach with singles, doubles, and triples in the bond-breaking region. Calculations of the activation enthalpy for the thermal isomerizations of cyclopropane involving trimethylene suggest that CR-CC(2,3) may be applicable to biradicals. (c) 2005 Elsevier B.V. All rights reserved.