Calculation of hyperfine coupling constants

Abstract

The hyperfine coupling constant for the nitrogen atom is evaluated by large-scale MRD-CI calculations. A detailed analysis of the charge density at the nucleus and the spin polarization in the 1s and 2s shell as a function of various technical parameters is undertaken. Various (s, p) AO basis sets and the influence of correlation orbitals is investigated as well as selection threshold and other properties in CI calculations. The best value, obtained for the isotropic hyperfine coupling constant in an s, p, d basis, based on theoretical judgment of ‘best’ quantities, is 9·9 MHz compared to 10·4509 MHz.