Variational calculations of the spin-spin coupling constant of hydrogen deuteride
Date
1979
Authors
Romaniuk, Anita Louise
Journal Title
Journal ISSN
Volume Title
Publisher
Abstract
There does not exist, at present, any definitive method of calculating nuclear spin-spin coupling constants. The main contribution to nuclear spin-spin coupling between hydrogen atoms is due to what is called "Fermi contact" interaction. Unfortunately the traditional operator used to represent this interaction is valid to only first order in perturbation theory and results in infinite second order self-coupling energies when either perturbation or perturbation-variation methods are applied. Phenomenological operators have been developed which remove the singularities at the nucleus which cause the diverging second order energy.
This thesis summarizes general nuclear spin-spin coupling theory and the derivation of appropriate operators, reviews previous work in this area, and presents a number of variational calculations of the Fermi contact part of the spin-spin coupling constant of hydrogen deuteride, all using a phenomenological operator developed by T.W. Dingle. There were two different approaches to the problem:
1) The first set of calculations used a one electron approximation which allowed comparison with previous work reported by other researchers who used a similar operator.
2) The second set of calculations used a more accurate method that allowed for the retention of two electron interaction terms.
While the one-electron calculations gave good results under specific constraints, the two-electron calculations yielded rather poor results. The trial wave functions used in the latter instance were probably inadequate to describe the effect of spin-spin coupling on the electronic charge distribution in the molecule. A discussion of the criteria which should be used to select such a wave function and some tentative proposals as to the form of the wave function are presented at the end of the thesis.