Multireference state-specific coupled-cluster methods. State-of-the-art and perspectives

Vladimir V. Ivanov, Dmitry I. Lyakh, Ludwik Adamowicz

Research output: Contribution to journalArticlepeer-review

43 Scopus citations


This work reviews the state-specific multireference coupled-cluster (CC) approaches which have been developed as approximate methods for performing high-level quantum mechanical calculations on quasidegenerate ground and excited states of atomic and molecular systems. The term "quasidegenerate" refers to a state that cannot be described even in the first approximation by a single-determinant wavefunction (a Slater determinant), but requires two or more determinants for this purpose. The main challenge with applying the coupled-cluster theory to such states is in describing the electron correlation effects in the wavefunctions representing these states in a manner that is size-extensive, yet accurate and simple enough so the method can be routinely applied to small and medium-size molecular systems. We are describing how this can be accomplished within a theory that focuses on only one state of the system in a single CC calculation (the state-specific theory).

Original languageEnglish (US)
Pages (from-to)2355-2370
Number of pages16
JournalPhysical Chemistry Chemical Physics
Issue number14
StatePublished - 2009

ASJC Scopus subject areas

  • Physics and Astronomy(all)
  • Physical and Theoretical Chemistry


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