Hartree–Fock and density functional complete basis-set (CBS) predicted nuclear shielding anisotropy and shielding tensor components

Abstract

The nuclear shielding anisotropy and shielding tensor components calculated using the hybrid density functional B3PW91 are reported for a model set of compounds comprised of N 2, NH 3, CH 4, C 2H 4, HCN and CH 3CN. An estimation of density functional theory (DFT) and Hartree–Fock complete basis-set limit (CBS) parameters from a 2 (3) point exact fit vs. least-squares fit was obtained with the cc-pV xZ and aug-cc-pV xZ basis sets ( x= D, T, Q, 5, 6). Both Hartree–Fock- and DFT-predicted CBS shielding anisotropies and shielding tensor components of the model molecules were in reasonable agreement with available experimental data. The utility of using a limited CBS approach for calculating accurate anisotropic shielding parameters of larger molecules as complementary methods to solid-state NMR is proposed.