Four-component relativistic theory for nuclear magnetic shielding constants: The orbital decomposition approach

The authors present a scheme to simplify four-component relativistic calculations of nuclear magnetic shielding constants. The central idea is to decompose each first order orbital into two terms, one is magnetically balanced and directly leads to the diamagnetic term, and the other is, to leading order of relativity, kinetically balanced and can therefore simply be represented in the basis of unperturbed positive energy states. As a matrix formulation, the present approach is far simpler than other operator theories. Combined with the Dirac-Kohn-Sham ansatz, the nuclear magnetic shielding constants for the Kr, Xe, and Rn atoms as well as the HBr and HI molecules are calculated, and the results compare favorably with those of other schemes. (c) 2007 American Institute of Physics.