NEW OPERATORS FOR CALCULATION OF INDIRECT NUCLEAR SPIN-SPIN COUPLING-CONSTANTS

The Fermi contact interaction, which makes an important contribution t o indirect nuclear spin-spin coupling constants, is sensitive to the e lectronic behavior at the positions of the coupled nuclei. Unfortunate ly, these regions are often not described well in commonly used molecu lar wave functions. It is shown that the delta function operators whic h formally represent this interaction in such second-order properties can be replaced by certain global operators in a manner analogous to t hat previously derived for first-order properties. It is further argue d that two specific choices of the new operators that have previously been demonstrated to be very useful for the calculation of isotropic h yperfine coupling constants may also be valuable in improving the accu racy of indirect nuclear spin-spin coupling constant calculations. Ill ustrative calculations are presented for HD withencouraging results. ( C) 1997 American Institute of Physics.