These tools will no longer be maintained as of December 31, 2024. Archived website can be found here. PubMed4Hh GitHub repository can be found here. Contact NLM Customer Service if you have questions.


Pubmed for Handhelds

PUBMED FOR HANDHELDS

Search MEDLINE/PubMed

  • Title: General-model-space state-universal coupled-cluster methods for excited states: diagonal noniterative triple corrections.
    Author: Li X, Paldus J.
    Journal: J Chem Phys; 2006 Jan 21; 124(3):034112. PubMed ID: 16438572.
    Abstract:
    The recently developed multireference, general-model-space, state-universal coupled-cluster approach considering singles and doubles (GMS SU CCSD) has been extended to account perturbatively for triples, similar to the ubiquitous single-reference CCSD(T) method. The effectiveness of this extension in handling of excited states and its ability to account for the static and nondynamic correlation effects when considering spin- and/or space-symmetry degenerate levels within the spin-orbital formalism is examined on the example of low-lying excitation energies of the C2, N2, and CO molecules and a comparison is made with the (N,N)-CCSD method used for the same purpose. It is shown that while the triple corrections are very effective in improving the absolute energies, they have only a modest effect on the corresponding excitation energies, which may be even detrimental if both the ground- and excited-state levels cannot be given a balanced treatment. While the triple corrections help to avoid the symmetry-breaking effects arising due to the use of the spin-orbital formalism, they are much less effective in this regard than the (N,N)-CCSD approach.
    [Abstract] [Full Text] [Related] [New Search]