CONTRIBUTION OF MOLECULAR VIBRATIONS TO CALCULATED SPIN-SPIN COUPLING-CONSTANTS - COMPARISON OF DIFFERENT COMMONLY-USED METHODS

The different methods commonly used to determine vibrational corrections to the calculated coupling constants, J, are compared, with reference to the HD and HF molecules. Calculations are carried out using ab initio and semi-empirical FPT INDO methods. It is found that the dependence of J on the interatomic distance given by the FPT INDO method is in marked disagreement with that predicted by ab initio methods. It is also found that vibrational corrections depend strongly on the method of vibrational averaging employed. The results display the need for experiments to determine the dependence of coupling constants on interatomic distances. © 1979.