Local spin from strongly orthogonal geminal wavefunctions

Covalent bond dissociation is examined by three geminal-based theories. One approach (antisymmetrised product of strongly orthogonal geminals) assumes purely singlet geminals, while two others operate with mixtures of singlets and triplets (cf. restricted-unrestricted strongly orthogonal singlet-typ...

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Bibliographic Details
Published in:Molecular physics 2015-02, Vol.113 (3-4), p.249-259
Main Authors: Jeszenszki, Péter, Rassolov, Vitaly, Surján, Péter R., Szabados, Ágnes
Format: Article
Language:English
Subjects:
Atomic structure
Contamination
Covalent bonds
geminal
Joining
local spin
Molecular physics
Molecular structure
singlet coupling
spin unrestricted
strong orthogonality
Switching
Wavefunctions
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Summary:Covalent bond dissociation is examined by three geminal-based theories. One approach (antisymmetrised product of strongly orthogonal geminals) assumes purely singlet geminals, while two others operate with mixtures of singlets and triplets (cf. restricted-unrestricted strongly orthogonal singlet-type geminals, hereafter RUSSG). The RUSSG is the wavefunction in the second method. It is spin contaminated. The spin contamination of RUSSG is projected out in a spin-purification step in the third method. Description of local (i.e. atomic) spin by geminal-based theories is examined. Prototype systems showing the deficiency of singlet coupling are taken as test cases. We find that the local spin of equilibrium structures is correctly described by purely singlet geminals. Triplet geminals are shown to be essential for the description of local spin when dissociating multiple bonds, or switching between two Lewis structures of the same molecule.
ISSN:0026-8976
1362-3028
DOI:10.1080/00268976.2014.936919