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dc.contributor.authorBučinský, Lukáš
dc.contributor.authorMalček, Michal
dc.contributor.authorBiskupič, Stanislav
dc.contributor.authorJayatilaka, Dylan
dc.contributor.authorBüchel, Gabriel E.
dc.contributor.authorArion, Vladimir B.
dc.date.accessioned2015-05-17T20:28:35Z
dc.date.available2015-05-17T20:28:35Z
dc.date.issued2015-05-11
dc.identifier.citationSpin contamination analogy, Kramers pairs symmetry and spin density representations at the 2-component unrestricted Hartree-Fock level of theory 2015 Computational and Theoretical Chemistry
dc.identifier.issn2210271X
dc.identifier.doi10.1016/j.comptc.2015.04.019
dc.identifier.urihttp://hdl.handle.net/10754/553011
dc.description.abstract"Kramers pairs symmetry breaking" is evaluated at the 2-component (2c) Kramers unrestricted and/or general complex Hartree-Fock (GCHF) level of theory, and its analogy with "spin contamination" at the 1-component (1c) unrestricted Hartree-Fock (UHF) level of theory is emphasized. The GCHF "Kramers pairs symmetry breaking" evaluation is using the square of overlaps between the set of occupied spinorbitals with the projected set of Kramers pairs. In the same fashion, overlaps between α and β orbitals are used in the evaluation of "spin contamination" at the UHF level of theory. In this manner, UHF Š2 expectation value is made formally extended to the GCHF case. The directly evaluated GCHF expectation value of the Š2 operator is considered for completeness. It is found that the 2c GCHF Kramers pairs symmetry breaking has a very similar extent in comparison to the 1c UHF spin contamination. Thus higher excited states contributions to the 1c and 2c unrestricted wave functions of open shell systems have almost the same extent and physical consequences. Moreover, it is formally shown that a single determinant wave function in the restricted open shell Kramers case has the expectation value of K2 operator equal to the negative number of open shell electrons, while the eigenvalue of K2 for the series of simple systems (H, He, He*-triplet, Li and Li*-quartet) are found to be equal to minus the square of the number of open shell electrons. The concept of unpaired electron density is extended to the GCHF regime and compared to UHF and restricted open shell Hartree-Fock spin density. The "collinear" and "noncollinear" analogs of spin density at the GCHF level of theory are considered as well. Spin contamination and/or Kramers pairs symmetry breaking, spin populations and spin densities are considered for H2O+, Cl, HCl+, phenoxyl radical (C6H5O) as well as for Cu, Cu2+, Fe and the [OsCl5(1H-pyrazole)]- anion. The 1c and 2c unpaired electron density representation is found useful for visualization and/or representation of spin density. © 2015 Elsevier B.V.
dc.publisherElsevier BV
dc.relation.urlhttp://linkinghub.elsevier.com/retrieve/pii/S2210271X15001760
dc.rightsNOTICE: this is the author’s version of a work that was accepted for publication in Computational and Theoretical Chemistry. Changes resulting from the publishing process, such as peer review, editing, corrections, structural formatting, and other quality control mechanisms may not be reflected in this document. Changes may have been made to this work since it was submitted for publication. A definitive version was subsequently published in Computational and Theoretical Chemistry, 11 May 2015. DOI: 10.1016/j.comptc.2015.04.019
dc.subjectSpin contamination
dc.subjectKramers pair
dc.subjectSpin density
dc.subjectKramers unrestricted
dc.subject2-component
dc.subjectUnpaired electron
dc.subjectGeneral complex
dc.titleSpin contamination analogy, Kramers pairs symmetry and spin density representations at the 2-component unrestricted Hartree-Fock level of theory
dc.typeArticle
dc.contributor.departmentPhysical Sciences and Engineering (PSE) Division
dc.contributor.departmentKAUST Catalysis Center (KCC)
dc.identifier.journalComputational and Theoretical Chemistry
dc.eprint.versionPost-print
dc.contributor.institutionInstitute of Physical Chemistry and Chemical Physics FCHPT, Slovak University of Technology, Radlinskeho 9, Bratislava, SK-812 37, Slovakia
dc.contributor.institutionDepartment of Chemistry, University of Western Australia, 35 Stirling Hwy, Crawley WA 6009, Australia
dc.contributor.institutionUniversity of Vienna, Institute of Inorganic Chemistry, Währinger Str. 42, A-1090 Vienna, Austria
kaust.personBüchel, Gabriel E.
refterms.dateFOA2017-05-11T00:00:00Z


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