Coupled-cluster method truncated at quadruples

Nevin Oliphant, Ludwik Adamowicz

Research output: Contribution to journalArticlepeer-review

206 Scopus citations


The coupled-cluster (CC) equations including single, double, triple, and quadruple excitation amplitudes (CCSDTQ) are derived diagramatically, and the complete set of CCSDTQ equations are presented. These equations have been programmed and an iterative reduced linear equation method is used to solve these equations. The potential curves for the dissociation of a model system with a single bond (Li2 and LiH) is calculated using CC doubles (CCD), singles and doubles (CCSD), singles, doubles, and triples (CCSDT), and CCSDTQ. These calculations demonstrate the magnitude of the CC contributions arising from single, double, triple, and quadruple excitation amplitudes to the stretching of a chemical bond.

Original languageEnglish (US)
Pages (from-to)6645-6651
Number of pages7
JournalThe Journal of chemical physics
Issue number9
StatePublished - 1991

ASJC Scopus subject areas

  • General Physics and Astronomy
  • Physical and Theoretical Chemistry


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