Sum-over-states density functional perturbation theory: Prediction of reliable 13C, 15N, and 17O nuclear magnetic resonance chemical shifts

Sum-over-states density functional perturbation theory �SOS-DFPT� has been used to calculate 13C, 15N, and 17O NMR chemical shifts of 20 molecules, for which accurate experimental gas-phase values are available. Compared to Hartree–Fock �HF�, SOS-DFPT leads to improved chemical shift values and approaches the degree of accuracy obtained with second order Mo”ller–Plesset perturbation theory �MP2�. This is particularly true in the case of 15N chemical shifts where SOS-DFPT performs even better than MP2. Additional improvements of SOS-DFPT chemical shifts can be obtained by empirically correcting diamagnetic and paramagnetic contributions to compensate for deficiencies which are typical of DFT. © 1996 American Institute of Physics. �S0021-9606�96�01544-9�