Calculation of hyperfine splitting constants with Slaterhyphen;type cusp basis by the symmetry adapted clusterhyphen;configuration interaction theory

摘要

A method of calculating hyperfine splitting constants (hfsc) of openhyphen;shell radicals is reported. Since the hfsc reflects a very local property of the wave function at the position of the nuclei, we use Slaterhyphen;type orbitals (STOs) which have cusps at the centers. Spin correlation (spin polarization) and electron correlation are taken into account with the use of the SAChyphen;CI (symmetry adapted clusterhyphen;configuration interaction) theory. Configuration selection is not done since energy and spin density are very different properties. The dimensions of the matrices involved in the SAChyphen;CI method are small enough to permit such a procedure. The integrals necessary for the SCF and SAChyphen;CI methods are calculated by the STOhyphen;6G method with the use of the available Gaussian program, and the hfscrsquo;s and the cusp values are calculated from the original STOs. Several STOs are examined for H+2and H2O+. The resultant standard method is applied to the organic pgr; and sgr; radicals CH3, CH3CH2, CH3NH, CH3O, CH3OCH+3, H2CO+, CH2CH, and HCO. The present results of hfscrsquo;s show generally better agreement with experiment than the previous calculations based on the Gaussianhyphen;type orbitals (GTOs). In particular, the present results are free from the theoretical dilemma seen for the GTO calculations that a variationally better wave function does not necessarily give a better hfsc. This is important in developing a reliable theory for calculating hfscrsquo;s.