Particle-particle and quasiparticle random phase approximations: Connections to coupled cluster theory

dc.citation.journalTitleThe Journal of Chemical Physicsen_US
dc.contributor.authorScuseria, Gustavo E.en_US
dc.contributor.authorHenderson, Thomas M.en_US
dc.contributor.authorBulik, Ireneusz W.en_US
dc.description.abstractWe establish a formal connection between the particle-particle (pp) random phase approximation (RPA) and the ladder channel of the coupled cluster doubles (CCD) equations. The relationship between RPA and CCD is best understood within a Bogoliubov quasiparticle (qp) RPA formalism. This work is a follow-up to our previous formal proof on the connection between particle-hole (ph) RPA and ring-CCD. Whereas RPA is a quasibosonic approximation, CC theory is a “correct bosonization” in the sense that the wavefunction and Hilbert space are exactly fermionic, yet the amplitude equations can be interpreted as adding different quasibosonic RPA channels together. Coupled cluster theory achieves this goal by interacting the ph (ring) and pp (ladder) diagrams via a third channel that we here call “crossed-ring” whose presence allows for full fermionic antisymmetry. Additionally, coupled cluster incorporates what we call “mosaic” terms which can be absorbed into defining a new effective one-body Hamiltonian. The inclusion of these mosaic terms seems to be quite important. The pp-RPA and qp-RPA equations are textbook material in nuclear structure physics but are largely unknown in quantum chemistry, where particle number fluctuations and Bogoliubov determinants are rarely used. We believe that the ideas and connections discussed in this paper may help design improved ways of incorporating RPA correlation into density functionals based on a CC perspective.en_US
dc.identifier.citationScuseria, Gustavo E., Henderson, Thomas M. and Bulik, Ireneusz W.. "Particle-particle and quasiparticle random phase approximations: Connections to coupled cluster theory." <i>The Journal of Chemical Physics,</i> 139, no. 10 (2013) American Institute of Physics:
dc.publisherAmerican Institute of Physics
dc.rightsArticle is made available in accordance with the publisher's policy and may be subject to US copyright law. Please refer to the publisher's site for terms of use.
dc.titleParticle-particle and quasiparticle random phase approximations: Connections to coupled cluster theoryen_US
dc.typeJournal articleen_US
dc.type.publicationpublisher versionen_US
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