MULTICONFIGURATIONAL SELF-CONSISTENT-FIELD CALCULATIONS OF NUCLEAR-MAGNETIC-RESONANCE INDIRECT SPIN-SPIN COUPLING-CONSTANTS

Ab initio calculations of all the nuclear magnetic resonance (NMR) ind irect nuclear spin-spin coupling constants in the HN3 molecule and in four isomers of CH2N2 are described. For each molecule, SCF and two mu lticonfiguration self-consistent field (MCSCF) wave functions that tak e into account valence shell correlation effects are applied. All mech anisms contributing to the coupling constants are included. While the SCF results are meaningless, the agreement of the correlated values wi th those known from experiment is satisfactory. Our most accurate calc ulations are carried out with the wave functions previously used succe ssfully to compute the NMR shielding constants, All parameters determi ning the NMR spectra of these molecules have thus been obtained at uni form accuracy from the same reference wave function.