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

Ab initio calculations of all the nuclear magnetic resonance (NMR) indirect nuclear spin-spin coupling constants in the HN3 molecule and in four isomers of CH2N2 are described. For each molecule, SCF and two multiconfiguration self-consistent field (MCSCF) wave functions that take into account valence shell correlation effects are applied. All mechanisms contributing to the coupling constants are included. While the SCF results are meaningless, the agreement of the correlated values with those known from experiment is satisfactory. Our most accurate calculations are carried out with the wave functions previously used successfully to compute the NMR shielding constants, All parameters determining the NMR spectra of these molecules have thus been obtained at uniform accuracy from the same reference wave function.