Comparison of NMR Shieldings Calculated from Hartree−Fock and Density Functional Wave Functions Using Gauge-Including Atomic Orbitals

A numerically accurate implementation of the gauge-including atomic orbital method for the calculation of NMR shieldings in density functional theory (DFT) is presented. Results calculated by this method are compared with results of SCF and accurate coupled cluster calculations for eight small molecules. Three sets of DFT results, obtained using different exchange-correlation functionals, are further compared with each other, with the SCF data, and with experiment for a set of 10 somewhat larger organic molecules. The DFT values show a modest improvement compared to SCF theory. Potential computational savings using density functional theory are discussed.