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dc.contributor.authorBytautas, Laimutis
Scuseria, Gustavo E.
Ruedenberg, Klaus
dc.date.accessioned 2017-06-05T17:33:45Z
dc.date.available 2017-06-05T17:33:45Z
dc.date.issued 2015
dc.identifier.citation Bytautas, Laimutis, Scuseria, Gustavo E. and Ruedenberg, Klaus. "Seniority number description of potential energy surfaces: Symmetric dissociation of water, N2, C2, and Be2." The Journal of Chemical Physics, 143, no. 9 (2015) AIP Publishing LLC.: http://dx.doi.org/10.1063/1.4929904.
dc.identifier.urihttps://hdl.handle.net/1911/94775
dc.description.abstract The present study further explores the concept of the seniority number (Ω) by examining different configuration interaction (CI) truncation strategies in generating compact wave functions in a systematic way. While the role of Ω in addressing static (strong) correlation problem has been addressed in numerous previous studies, the usefulness of seniority number in describing weak (dynamic) correlation has not been investigated in a systematic way. Thus, the overall objective in the present work is to investigate the role of Ω in addressing also dynamic electron correlation in addition to the static correlation. Two systematic CI truncation strategies are compared beyond minimal basis sets and full valence active spaces. One approach is based on the seniority number (defined as the total number of singly occupied orbitals in a determinant) and another is based on an excitation-level limitation. In addition, molecular orbitals are energy-optimized using multiconfigurational-self-consistent-field procedure for all these wave functions. The test cases include the symmetric dissociation of water (6-31G), N2 (6-31G), C2 (6-31G), and Be2 (cc-pVTZ). We find that the potential energy profile for H2O dissociation can be reasonably well described using only the Ω = 0 sector of the CI wave function. For the Be2 case, we show that the full CI potential energy curve (cc-pVTZ) is almost exactly reproduced using either Ω-based (including configurations having up to Ω = 2 in the virtual-orbital-space) or excitation-based (up to single-plus-double-substitutions) selection methods, both out of a full-valence-reference function. Finally, in dissociation cases of N2 and C2, we shall also consider novel hybrid wave functions obtained by a union of a set of CI configurations representing the full valence space and a set of CI configurations where seniority-number restriction is imposed for a complete set (full-valence-space and virtual) of correlated molecular orbitals, simultaneously. We discuss the usefulness of the seniority number concept in addressing both static and dynamic electron correlation problems along dissociation paths.
dc.language.iso eng
dc.publisher AIP Publishing LLC.
dc.rights Article 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.title Seniority number description of potential energy surfaces: Symmetric dissociation of water, N2, C2, and Be2
dc.type Journal article
dc.citation.journalTitle The Journal of Chemical Physics
dc.citation.volumeNumber 143
dc.citation.issueNumber 9
dc.type.dcmi Text
dc.identifier.doihttp://dx.doi.org/10.1063/1.4929904
dc.identifier.pmid 26342357
dc.type.publication publisher version
dc.citation.articleNumber 094105


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