Effect of rotation and vibration on nuclear magnetic resonance chemical shifts: Density functional theory calculations

The effect of rotation and vibration on the nuclear magnetic resonance ~NMR! shielding constants was computed for HF, F2, N2, CO, and HBr. The shielding constants for H, C, N, O, and F nuclei were calculated using sum-over-states density functional perturbation theory ~SOS-DFPT!. Diatomic ro-vibrational states were calculated from a discrete variable representation using Morse potentials and potential curves calculated with density functional theory. Our ro-vibrational corrections to shielding constants for HF, CO, F2, and N2 molecules are in good agreement with experimental data and CCSD~T! calculations. These results together with satisfactory first and second derivatives of the shielding constants with respect to interatomic distances confirm that the shielding surfaces produced by the SOS-DFPT method are of good accuracy, providing reassurance of the use of these methods for more complex systems. The unusual temperature dependence of the hydrogen chemical shift in HBr and a first attempt to include both relativistic spin-orbit and ro-vibration effects are discussed. © 1999 American Institute of Physics. @S0021-9606~99!30314-7#