Spin density in first-row atoms from the Hiller-Sucher-Feinberg identity

Summary The performance of delta function and Hiller-Sucher-Feinberg (HSF) operators is compared for calculations of the electronic spin density at the nucleus, which determines the observed Fermi contact hyperfine splitting. Calculations are performed on the ground states of the first-row open-shell atoms boron through fluorine. The wavefunctions include low order spin polarization effects calculated through the multiconfigurational self-consistent-field procedure. It is shown that while delta function and HSF operators give nearly the same results when essentially exact numerical grid methods are used, the HSF operator gives a significant advantage when contracted Gaussian type basis sets are utilized.