HARTREE-FOCK AND 2ND-ORDER MOLLER-PLESSET PERTURBATION-THEORY CALCULATIONS OF THE P-31 NUCLEAR-MAGNETIC-RESONANCE SHIELDING TENSOR IN PH3

The P-31 shielding tensor for PH3 has been calculated without electron correlation (self-consistent field) and with electron correlation (se cond-order Mollet-Plesset) using the gauge including atomic orbital me thod. The best results obtained for the absolute isotropic chemical sh ielding constant (608.09 ppm) and chemical shielding anisotropy (64.54 ppm) compare quite favorably with the experimental values of 600 and 64.5 ppm. The contribution of electron correlation to the absolute shi elding value has been found to be significant. The convergence of the calculated shielding tensor with respect to the quality of the basis s et employed and the importance of d and f polarization orbitals are di scussed.