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Bulletin of the Korean Chemical Society (BKCS)

ISSN 0253-2964(Print)
ISSN 1229-5949(Online)
Volume 22, Number 9
BKCSDE 22(9)
September 20, 2001 

 
Title
Effects of the Magnetic Part of the Breit Term on Bonding : Model Calculations with Small Diatomic Molecules
Author
Seol Ryu, Kyoung K. Baeck, Young-Kyu Han, Yoon Sup Lee
Keywords
Dirac-Fock calculation, Relativistic effects, Breit interactions, Dirac-Coulomb-Magnetic Hamiltonian.
Abstract
Model calculations for small molecules Li2, F2, LiF and BF have been performed at the Dirac-Fock level of theory using Dirac-Coulomb and Dirac-Coulomb-Magnetic Hamiltonians with various basis sets. In order to understand what may happen when the relativity becomes significant, the value of c, speed of light, is varied from the true value of 137.036 a.u. to 105 (nonrelativistic case) and also to 50 and 20 a.u. (exaggerated relativistic cases). Qualitative trends are discussed with special emphasis on the effect of the magnetic part of the Breit interaction term. The known relativistic effects on bonding such as the bond length contraction or expansion are demonstrated in this model study. Total energy, π-orbital splitting, bond length, bond dissociation energy and dipole moment are calculated, and shown to be modified in a uniform direction by the effect of the magnetic term. Inclusion of the magnetic term raises the total energy, increases the bond length, reduces the π-orbital splitting, increases the bond dissociation energy, and mitigates the changes in dipole moment caused by the Dirac term.
Page
969 - 974
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