Spin densities of first-row atoms calculated from polarization wave functions with accurate numerical methods.

Abstract

Fermi contact spin densities of the first-row atoms B--F having open-shell p electrons are systematically calculated with simple, physically interpretable wave-function models that include only the dominant configurations together with relevant single excitations that describe polarization effects. All orbitals involved are optimized self-consistently by accurate numerical grid methods to obviate any questions about basis-set incompleteness. It is found that spin polarization of the 1s, 2s, and 2p shells (the latter for oxygen and fluorine only) together with orbital polarization of the 2s shell are the important effects. Core and valence contributions are separately large in magnitude, but nearly cancel one another leading to much smaller net spin densities. The results show good semiquantitative agreement with experiment, implying that true electron-correlation effects play a secondary role in determining the spin densities of these first-row atoms.