Sum-over-states calculation of the nuclear spin-spin coupling constants

Nuclear spin-spin coupling constants calculated using the sum-over-states ( SOS) expansions were compared to experimental values and usual coupled-pert urbed (CP) calculations. Rigid Kohn-Sham orbitals obtained from a hybrid de nsity functional were used in the SOS model. Its accuracy for small molecul es is comparable with the CP results, nevertheless calculated constants wer e uniformly underestimated. However, the SOS scheme is less limited by mole cular size and can be applied for bigger systems than the CP method, as doc umented on the proton-proton coupling constants in alpha-pinene, beta-pinen e, and camphor molecules. (C) 1999 American Institute of Physics. [S0021-96 06(99)30506-7].