CALCULATION OF NUCLEAR SPIN-SPIN COUPLINGS .7. ELECTRON CORRELATION-EFFECTS ON THE 5 COUPLING MECHANISMS

Electron correlation effects on the five mechanisms in the indirect nuclear spin-spin coupling tensors are computed for H F-19, H-2 O-17, (NH3)-N-14, (CH4)-C-13, H Cl-35, (SH2)-S-33, (PH3)-P-31, and (SiH4)-Si-29. The five coupling mechanisms consist of Fermi-contact (FC), spin-dipole (SD), Fermi-contact and spin-dipole cross term (FC/SD), orbital paramagnetic (OP), and orbital diamagnetic (OD) terms. Electron correlation contributions through the second order are calculated by the finite-field many-body perturbation theory (FF-MBPT). The results show an extremely large contribution of the (FC/SD) cross term to the anisotropic part of the couplings. The FC contribution is dominant in the isotropic part, but the OP term is considerable in HF, HCl, and H2O. Electron correlation effects are large in the FC contribution. They are small, but not negligible, in the other terms except in the OD term.