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Title: Singlet-paired coupled cluster theory for open shells

Restricted single-reference coupled cluster theory truncated to single and double excitations accurately describes weakly correlated systems, but often breaks down in the presence of static or strong correlation. Good coupled cluster energies in the presence of degeneracies can be obtained by using a symmetry-broken reference, such as unrestricted Hartree-Fock, but at the cost of good quantum numbers. A large body of work has shown that modifying the coupled cluster ansatz allows for the treatment of strong correlation within a single-reference, symmetry-adapted framework. The recently introduced singlet-paired coupled cluster doubles (CCD0) method is one such model, which recovers correct behavior for strong correlation without requiring symmetry breaking in the reference. In this, we extend singlet-paired coupled cluster for application to open shells via restricted open-shell singlet-paired coupled cluster singles and doubles (ROCCSD0). The ROCCSD0 approach retains the benefits of standard coupled cluster theory and recovers correct behavior for strongly correlated, open-shell systems using a spin-preserving ROHF reference.
Authors:
ORCiD logo [1] ;  [2] ;  [2]
  1. Rice Univ., Houston, TX (United States). Dept. of Chemistry
  2. Rice Univ., Houston, TX (United States). Dept. of Chemistry and Dept. of Physics and Astronomy
Publication Date:
Grant/Contract Number:
FG02-04ER15523; DGE-1450681
Type:
Accepted Manuscript
Journal Name:
Journal of Chemical Physics
Additional Journal Information:
Journal Volume: 144; Journal Issue: 24; Journal ID: ISSN 0021-9606
Publisher:
American Institute of Physics (AIP)
Research Org:
Rice Univ., Houston, TX (United States)
Sponsoring Org:
USDOE Office of Science (SC), Basic Energy Sciences (BES) (SC-22); Welch Foundation; National Science Foundation (NSF)
Country of Publication:
United States
Language:
English
Subject:
37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY; 74 ATOMIC AND MOLECULAR PHYSICS; excited states; coupled cluster; basis sets; configuration interactions; electron correlation calculations; wave functions; charge coupled devices; dissociation energies
OSTI Identifier:
1467828
Alternate Identifier(s):
OSTI ID: 1259983

Gomez, John A., Henderson, Thomas M., and Scuseria, Gustavo E.. Singlet-paired coupled cluster theory for open shells. United States: N. p., Web. doi:10.1063/1.4954891.
Gomez, John A., Henderson, Thomas M., & Scuseria, Gustavo E.. Singlet-paired coupled cluster theory for open shells. United States. doi:10.1063/1.4954891.
Gomez, John A., Henderson, Thomas M., and Scuseria, Gustavo E.. 2016. "Singlet-paired coupled cluster theory for open shells". United States. doi:10.1063/1.4954891. https://www.osti.gov/servlets/purl/1467828.
@article{osti_1467828,
title = {Singlet-paired coupled cluster theory for open shells},
author = {Gomez, John A. and Henderson, Thomas M. and Scuseria, Gustavo E.},
abstractNote = {Restricted single-reference coupled cluster theory truncated to single and double excitations accurately describes weakly correlated systems, but often breaks down in the presence of static or strong correlation. Good coupled cluster energies in the presence of degeneracies can be obtained by using a symmetry-broken reference, such as unrestricted Hartree-Fock, but at the cost of good quantum numbers. A large body of work has shown that modifying the coupled cluster ansatz allows for the treatment of strong correlation within a single-reference, symmetry-adapted framework. The recently introduced singlet-paired coupled cluster doubles (CCD0) method is one such model, which recovers correct behavior for strong correlation without requiring symmetry breaking in the reference. In this, we extend singlet-paired coupled cluster for application to open shells via restricted open-shell singlet-paired coupled cluster singles and doubles (ROCCSD0). The ROCCSD0 approach retains the benefits of standard coupled cluster theory and recovers correct behavior for strongly correlated, open-shell systems using a spin-preserving ROHF reference.},
doi = {10.1063/1.4954891},
journal = {Journal of Chemical Physics},
number = 24,
volume = 144,
place = {United States},
year = {2016},
month = {6}
}